10634: Added the capability to inject boto3 client in SagemakerEndpointEmbeddings (#12146)

**Description: Allow to inject boto3 client for Cross account access
type of scenarios in using SagemakerEndpointEmbeddings and also updated
the documentation for same in the sample notebook**

**Issue:SagemakerEndpointEmbeddings cross account capability #10634
#10184**

Dependencies: None
Tag maintainer:
Twitter handle:lethargicoder

Co-authored-by: Vikram(VS) <vssht@amazon.com>

libs/langchain/langchain/embeddings/sagemaker_endpoint.py

@@ -46,8 +46,18 @@ class SagemakerEndpointEmbeddings(BaseModel, Embeddings):
                 region_name=region_name,
                 credentials_profile_name=credentials_profile_name
             )
+
+            #Use with boto3 client
+            client = boto3.client(
+                        "sagemaker-runtime",
+                        region_name=region_name
+                    )
+            se = SagemakerEndpointEmbeddings(
+                endpoint_name=endpoint_name,
+                client=client
+            )
     """
-    client: Any  #: :meta private:
+    client: Any = None
 
     endpoint_name: str = ""
     """The name of the endpoint from the deployed Sagemaker model.
@@ -106,6 +116,10 @@ class SagemakerEndpointEmbeddings(BaseModel, Embeddings):
 
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
+        """Dont do anything if client provided externally"""
+        if values.get("client") is not None:
+            return values
+
         """Validate that AWS credentials to and python package exists in environment."""
         try:
             import boto3