diff --git a/google/cloud/servicecontrol_v1/services/quota_controller/async_client.py b/google/cloud/servicecontrol_v1/services/quota_controller/async_client.py
index d91c49b..8f5c00b 100644
--- a/google/cloud/servicecontrol_v1/services/quota_controller/async_client.py
+++ b/google/cloud/servicecontrol_v1/services/quota_controller/async_client.py
@@ -19,14 +19,17 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-from google.api_core.client_options import ClientOptions  # type: ignore
-from google.api_core import exceptions as core_exceptions  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import retry as retries  # type: ignore
+from google.api_core.client_options import ClientOptions
+from google.api_core import exceptions as core_exceptions
+from google.api_core import gapic_v1
+from google.api_core import retry as retries
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
-OptionalRetry = Union[retries.Retry, object]
+try:
+    OptionalRetry = Union[retries.Retry, gapic_v1.method._MethodDefault]
+except AttributeError:  # pragma: NO COVER
+    OptionalRetry = Union[retries.Retry, object]  # type: ignore
 
 from google.cloud.servicecontrol_v1.types import metric_value
 from google.cloud.servicecontrol_v1.types import quota_controller
diff --git a/google/cloud/servicecontrol_v1/services/quota_controller/client.py b/google/cloud/servicecontrol_v1/services/quota_controller/client.py
index cb4e64b..1e93602 100644
--- a/google/cloud/servicecontrol_v1/services/quota_controller/client.py
+++ b/google/cloud/servicecontrol_v1/services/quota_controller/client.py
@@ -14,23 +14,25 @@
 # limitations under the License.
 #
 from collections import OrderedDict
-from distutils import util
 import os
 import re
 from typing import Dict, Optional, Sequence, Tuple, Type, Union
 import pkg_resources
 
-from google.api_core import client_options as client_options_lib  # type: ignore
-from google.api_core import exceptions as core_exceptions  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import retry as retries  # type: ignore
+from google.api_core import client_options as client_options_lib
+from google.api_core import exceptions as core_exceptions
+from google.api_core import gapic_v1
+from google.api_core import retry as retries
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport import mtls  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
-OptionalRetry = Union[retries.Retry, object]
+try:
+    OptionalRetry = Union[retries.Retry, gapic_v1.method._MethodDefault]
+except AttributeError:  # pragma: NO COVER
+    OptionalRetry = Union[retries.Retry, object]  # type: ignore
 
 from google.cloud.servicecontrol_v1.types import metric_value
 from google.cloud.servicecontrol_v1.types import quota_controller
@@ -271,8 +273,15 @@ def __init__(
             client_options = client_options_lib.ClientOptions()
 
         # Create SSL credentials for mutual TLS if needed.
-        use_client_cert = bool(
-            util.strtobool(os.getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE", "false"))
+        if os.getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE", "false") not in (
+            "true",
+            "false",
+        ):
+            raise ValueError(
+                "Environment variable `GOOGLE_API_USE_CLIENT_CERTIFICATE` must be either `true` or `false`"
+            )
+        use_client_cert = (
+            os.getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE", "false") == "true"
         )
 
         client_cert_source_func = None
diff --git a/google/cloud/servicecontrol_v1/services/quota_controller/transports/base.py b/google/cloud/servicecontrol_v1/services/quota_controller/transports/base.py
index a3e7ff7..f4a8645 100644
--- a/google/cloud/servicecontrol_v1/services/quota_controller/transports/base.py
+++ b/google/cloud/servicecontrol_v1/services/quota_controller/transports/base.py
@@ -18,10 +18,10 @@
 import pkg_resources
 
 import google.auth  # type: ignore
-import google.api_core  # type: ignore
-from google.api_core import exceptions as core_exceptions  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import retry as retries  # type: ignore
+import google.api_core
+from google.api_core import exceptions as core_exceptions
+from google.api_core import gapic_v1
+from google.api_core import retry as retries
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
diff --git a/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc.py b/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc.py
index 86e4b17..e4775ac 100644
--- a/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc.py
+++ b/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc.py
@@ -16,8 +16,8 @@
 import warnings
 from typing import Callable, Dict, Optional, Sequence, Tuple, Union
 
-from google.api_core import grpc_helpers  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
+from google.api_core import grpc_helpers
+from google.api_core import gapic_v1
 import google.auth  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
diff --git a/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc_asyncio.py b/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc_asyncio.py
index e25b311..69c323e 100644
--- a/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc_asyncio.py
+++ b/google/cloud/servicecontrol_v1/services/quota_controller/transports/grpc_asyncio.py
@@ -16,8 +16,8 @@
 import warnings
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Tuple, Union
 
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import grpc_helpers_async  # type: ignore
+from google.api_core import gapic_v1
+from google.api_core import grpc_helpers_async
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
 
diff --git a/google/cloud/servicecontrol_v1/services/service_controller/async_client.py b/google/cloud/servicecontrol_v1/services/service_controller/async_client.py
index 1f13c8a..836dede 100644
--- a/google/cloud/servicecontrol_v1/services/service_controller/async_client.py
+++ b/google/cloud/servicecontrol_v1/services/service_controller/async_client.py
@@ -19,14 +19,17 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-from google.api_core.client_options import ClientOptions  # type: ignore
-from google.api_core import exceptions as core_exceptions  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import retry as retries  # type: ignore
+from google.api_core.client_options import ClientOptions
+from google.api_core import exceptions as core_exceptions
+from google.api_core import gapic_v1
+from google.api_core import retry as retries
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
-OptionalRetry = Union[retries.Retry, object]
+try:
+    OptionalRetry = Union[retries.Retry, gapic_v1.method._MethodDefault]
+except AttributeError:  # pragma: NO COVER
+    OptionalRetry = Union[retries.Retry, object]  # type: ignore
 
 from google.cloud.servicecontrol_v1.types import check_error
 from google.cloud.servicecontrol_v1.types import service_controller
diff --git a/google/cloud/servicecontrol_v1/services/service_controller/client.py b/google/cloud/servicecontrol_v1/services/service_controller/client.py
index 3b5f129..cd8d957 100644
--- a/google/cloud/servicecontrol_v1/services/service_controller/client.py
+++ b/google/cloud/servicecontrol_v1/services/service_controller/client.py
@@ -14,23 +14,25 @@
 # limitations under the License.
 #
 from collections import OrderedDict
-from distutils import util
 import os
 import re
 from typing import Dict, Optional, Sequence, Tuple, Type, Union
 import pkg_resources
 
-from google.api_core import client_options as client_options_lib  # type: ignore
-from google.api_core import exceptions as core_exceptions  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import retry as retries  # type: ignore
+from google.api_core import client_options as client_options_lib
+from google.api_core import exceptions as core_exceptions
+from google.api_core import gapic_v1
+from google.api_core import retry as retries
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport import mtls  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
-OptionalRetry = Union[retries.Retry, object]
+try:
+    OptionalRetry = Union[retries.Retry, gapic_v1.method._MethodDefault]
+except AttributeError:  # pragma: NO COVER
+    OptionalRetry = Union[retries.Retry, object]  # type: ignore
 
 from google.cloud.servicecontrol_v1.types import check_error
 from google.cloud.servicecontrol_v1.types import service_controller
@@ -273,8 +275,15 @@ def __init__(
             client_options = client_options_lib.ClientOptions()
 
         # Create SSL credentials for mutual TLS if needed.
-        use_client_cert = bool(
-            util.strtobool(os.getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE", "false"))
+        if os.getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE", "false") not in (
+            "true",
+            "false",
+        ):
+            raise ValueError(
+                "Environment variable `GOOGLE_API_USE_CLIENT_CERTIFICATE` must be either `true` or `false`"
+            )
+        use_client_cert = (
+            os.getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE", "false") == "true"
         )
 
         client_cert_source_func = None
diff --git a/google/cloud/servicecontrol_v1/services/service_controller/transports/base.py b/google/cloud/servicecontrol_v1/services/service_controller/transports/base.py
index 07eb753..d90451c 100644
--- a/google/cloud/servicecontrol_v1/services/service_controller/transports/base.py
+++ b/google/cloud/servicecontrol_v1/services/service_controller/transports/base.py
@@ -18,10 +18,10 @@
 import pkg_resources
 
 import google.auth  # type: ignore
-import google.api_core  # type: ignore
-from google.api_core import exceptions as core_exceptions  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import retry as retries  # type: ignore
+import google.api_core
+from google.api_core import exceptions as core_exceptions
+from google.api_core import gapic_v1
+from google.api_core import retry as retries
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
diff --git a/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc.py b/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc.py
index 7100c53..d22f6c5 100644
--- a/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc.py
+++ b/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc.py
@@ -16,8 +16,8 @@
 import warnings
 from typing import Callable, Dict, Optional, Sequence, Tuple, Union
 
-from google.api_core import grpc_helpers  # type: ignore
-from google.api_core import gapic_v1  # type: ignore
+from google.api_core import grpc_helpers
+from google.api_core import gapic_v1
 import google.auth  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
diff --git a/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc_asyncio.py b/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc_asyncio.py
index 46f953d..dc2f0a3 100644
--- a/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc_asyncio.py
+++ b/google/cloud/servicecontrol_v1/services/service_controller/transports/grpc_asyncio.py
@@ -16,8 +16,8 @@
 import warnings
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Tuple, Union
 
-from google.api_core import gapic_v1  # type: ignore
-from google.api_core import grpc_helpers_async  # type: ignore
+from google.api_core import gapic_v1
+from google.api_core import grpc_helpers_async
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
 
diff --git a/google/cloud/servicecontrol_v1/types/distribution.py b/google/cloud/servicecontrol_v1/types/distribution.py
index 22c57bd..e145d45 100644
--- a/google/cloud/servicecontrol_v1/types/distribution.py
+++ b/google/cloud/servicecontrol_v1/types/distribution.py
@@ -75,12 +75,15 @@ class Distribution(proto.Message):
             Any suffix of trailing zeros may be omitted.
         linear_buckets (google.cloud.servicecontrol_v1.types.Distribution.LinearBuckets):
             Buckets with constant width.
+
             This field is a member of `oneof`_ ``bucket_option``.
         exponential_buckets (google.cloud.servicecontrol_v1.types.Distribution.ExponentialBuckets):
             Buckets with exponentially growing width.
+
             This field is a member of `oneof`_ ``bucket_option``.
         explicit_buckets (google.cloud.servicecontrol_v1.types.Distribution.ExplicitBuckets):
             Buckets with arbitrary user-provided width.
+
             This field is a member of `oneof`_ ``bucket_option``.
         exemplars (Sequence[google.api.distribution_pb2.Exemplar]):
             Example points. Must be in increasing order of ``value``
diff --git a/google/cloud/servicecontrol_v1/types/log_entry.py b/google/cloud/servicecontrol_v1/types/log_entry.py
index dc8ec7f..edc058a 100644
--- a/google/cloud/servicecontrol_v1/types/log_entry.py
+++ b/google/cloud/servicecontrol_v1/types/log_entry.py
@@ -70,14 +70,17 @@ class LogEntry(proto.Message):
             The log entry payload, represented as a protocol buffer that
             is expressed as a JSON object. The only accepted type
             currently is [AuditLog][google.cloud.audit.AuditLog].
+
             This field is a member of `oneof`_ ``payload``.
         text_payload (str):
             The log entry payload, represented as a
             Unicode string (UTF-8).
+
             This field is a member of `oneof`_ ``payload``.
         struct_payload (google.protobuf.struct_pb2.Struct):
             The log entry payload, represented as a
             structure that is expressed as a JSON object.
+
             This field is a member of `oneof`_ ``payload``.
         operation (google.cloud.servicecontrol_v1.types.LogEntryOperation):
             Optional. Information about an operation
diff --git a/google/cloud/servicecontrol_v1/types/metric_value.py b/google/cloud/servicecontrol_v1/types/metric_value.py
index ed11979..219df73 100644
--- a/google/cloud/servicecontrol_v1/types/metric_value.py
+++ b/google/cloud/servicecontrol_v1/types/metric_value.py
@@ -55,18 +55,23 @@ class MetricValue(proto.Message):
             will be used.
         bool_value (bool):
             A boolean value.
+
             This field is a member of `oneof`_ ``value``.
         int64_value (int):
             A signed 64-bit integer value.
+
             This field is a member of `oneof`_ ``value``.
         double_value (float):
             A double precision floating point value.
+
             This field is a member of `oneof`_ ``value``.
         string_value (str):
             A text string value.
+
             This field is a member of `oneof`_ ``value``.
         distribution_value (google.cloud.servicecontrol_v1.types.Distribution):
             A distribution value.
+
             This field is a member of `oneof`_ ``value``.
     """