Skips creating boto client for Bedrock if passed in constructor (#5523)

# Skips creating boto client if passed in constructor
Current LLM and Embeddings class always creates a new boto client, even
if one is passed in a constructor. This blocks certain users from
passing in externally created boto clients, for example in SSO
authentication.

## Who can review?
@hwchase17 
@jasondotparse 
@rsgrewal-aws

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langchain/embeddings/bedrock.py

@@ -68,6 +68,10 @@ class BedrockEmbeddings(BaseModel, Embeddings):
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that AWS credentials to and python package exists in environment."""
+
+        if "client" in values:
+            return values
+
         try:
             import boto3
 

langchain/llms/bedrock.py

@@ -99,6 +99,11 @@ class Bedrock(LLM):
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that AWS credentials to and python package exists in environment."""
+
+        # Skip creating new client if passed in constructor
+        if "client" in values:
+            return values
+
         try:
             import boto3