fix: guard SageMaker-only methods in Bedrock mode

Address review feedback: In Bedrock mode, `self._sess` was never set,
so SageMaker-only methods would throw confusing AttributeErrors. Now:
- Initialize `_sess=None` and `_endpoint_name=None` in Bedrock mode
- Add `_require_sagemaker()` guard to connect_to_endpoint,
  create_endpoint, export_finetune, summarize, and delete_endpoint

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: fern-support

src/cohere/manually_maintained/cohere_aws/client.py

@@ -37,8 +37,12 @@ def __init__(
         elif self.mode == Mode.BEDROCK:
             self._client = lazy_boto3().client("bedrock-runtime", region_name=aws_region)
             self._service_client = lazy_boto3().client("bedrock", region_name=aws_region)
+            self._sess = None
+            self._endpoint_name = None
 
-
+    def _require_sagemaker(self) -> None:
+        if self.mode != Mode.SAGEMAKER:
+            raise CohereError("This method is only supported in SageMaker mode.")
 
     def _does_endpoint_exist(self, endpoint_name: str) -> bool:
         try:
@@ -56,6 +60,7 @@ def connect_to_endpoint(self, endpoint_name: str) -> None:
         Raises:
             CohereError: Connection to the endpoint failed.
         """
+        self._require_sagemaker()
         if not self._does_endpoint_exist(endpoint_name):
             raise CohereError(f"Endpoint {endpoint_name} does not exist.")
         self._endpoint_name = endpoint_name
@@ -143,6 +148,7 @@ def create_endpoint(
                 will be used to get the role. This should work when one uses the client inside SageMaker. If this errors
                 out, the default role "ServiceRoleSagemaker" will be used, which generally works outside of SageMaker.
         """
+        self._require_sagemaker()
         # First, check if endpoint already exists
         if self._does_endpoint_exist(endpoint_name):
             if recreate:
@@ -815,6 +821,7 @@ def export_finetune(
             This should work when one uses the client inside SageMaker. If this errors out,
             the default role "ServiceRoleSagemaker" will be used, which generally works outside SageMaker.
         """
+        self._require_sagemaker()
         if name == "model":
             raise ValueError("name cannot be 'model'")
 
@@ -958,6 +965,7 @@ def summarize(
         additional_command: Optional[str] = "",
         variant: Optional[str] = None
     ) -> Summary:
+        self._require_sagemaker()
 
         if self._endpoint_name is None:
             raise CohereError("No endpoint connected. "
@@ -999,6 +1007,7 @@ def summarize(
 
 
     def delete_endpoint(self) -> None:
+        self._require_sagemaker()
         if self._endpoint_name is None:
             raise CohereError("No endpoint connected.")
         try: