@staticmethod<EOL><INDENT>def _get_function_arn(uri_data):<DEDENT>
if not uri_data:<EOL><INDENT>return None<EOL><DEDENT>if LambdaUri._is_sub_intrinsic(uri_data):<EOL><INDENT>uri_data = LambdaUri._resolve_fn_sub(uri_data)<EOL>LOG.debug("<STR_LIT>", uri_data)<EOL><DEDENT>if not isinstance(uri_data, string_types):<EOL><INDENT>LOG.debug("<STR_LIT>", uri_data)<EOL>return None<EOL><DEDENT>matches = re.match(LambdaUri._REGEX_GET_FUNCTION_ARN, uri_data)<EOL>if not matches or not matches.groups():<EOL><INDENT>LOG.debug("<STR_LIT>", uri_data)<EOL>return None<EOL><DEDENT>groups = matches.groups()<EOL>return groups[<NUM_LIT:0>]<EOL>
Integration URI can be expressed in various shapes and forms. This method normalizes the Integration URI ARN
and returns the Lambda Function ARN. Here are the different forms of Integration URI ARN:

- String:
    - Fully resolved ARN
    - ARN with Stage Variables:
      Ex: arn:aws:apigateway:ap-southeast-2:lambda:path/2015-03-31/functions/arn:aws:lambda:ap-southeast-2:123456789012:function:${stageVariables.PostFunctionName}/invocations  # NOQA

- Dictionary: Usually contains intrinsic functions

    - Fn::Sub:
      Example:
      {
        "Fn::Sub":
          "arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${LambdaFunction.Arn}/invocations"
      }

    - Fn::Join: **Unsupported**. It is very hard to combine the joins into one string especially when
      certain properties are resolved only at runtime.

    - Ref, Fn::GetAtt: **Unsupported**. Impossible to use these intrinsics with integration URI. CFN doesn't
      support this functionality.

Note
~~~~
This method supports only a very restricted subset of intrinsic functions with Swagger document. This is the
best we can do without implementing a full blown intrinsic function resolution module.

Parameters
----------
uri_data : string or dict
    Value of Integration URI. It can either be a string or an intrinsic function that resolves to a string

Returns
-------
basestring or None
    Lambda Function ARN extracted from Integration URI. None, if it cannot get function Arn