code: def update_lambda_configuration(    self,
                                          lambda_arn,
                                          function_name,
                                          handler,
                                          description='Zappa Deployment',
                                          timeout=30,
                                          memory_size=512,
                                          publish=True,
                                          vpc_config=None,
                                          runtime='python2.7',
                                          aws_environment_variables=None,
                                          aws_kms_key_arn=None
                                      ):
          
          print("Updating Lambda function configuration..")
  
          if not vpc_config:
              vpc_config = {}
          if not self.credentials_arn:
              self.get_credentials_arn()
          if not aws_kms_key_arn:
              aws_kms_key_arn = ''
          if not aws_environment_variables:
              aws_environment_variables = {}
  
          # Check if there are any remote aws lambda env vars so they don't get trashed.
          # https://github.com/Miserlou/Zappa/issues/987,  Related: https://github.com/Miserlou/Zappa/issues/765
          lambda_aws_config = self.lambda_client.get_function_configuration(FunctionName=function_name)
          if "Environment" in lambda_aws_config:
              lambda_aws_environment_variables = lambda_aws_config["Environment"].get("Variables", {})
              # Append keys that are remote but not in settings file
              for key, value in lambda_aws_environment_variables.items():
                  if key not in aws_environment_variables:
                      aws_environment_variables[key] = value
  
          response = self.lambda_client.update_function_configuration(
              FunctionName=function_name,
              Runtime=runtime,
              Role=self.credentials_arn,
              Handler=handler,
              Description=description,
              Timeout=timeout,
              MemorySize=memory_size,
              VpcConfig=vpc_config,
              Environment={'Variables': aws_environment_variables},
              KMSKeyArn=aws_kms_key_arn,
              TracingConfig={
                  'Mode': 'Active' if self.xray_tracing else 'PassThrough'
              }
          )
  
          resource_arn = response['FunctionArn']
  
          if self.tags:
              self.lambda_client.tag_resource(Resource=resource_arn, Tags=self.tags)
  
          return resource_arn
docs: Given an existing function ARN, update the configuration variables.