Is this input data a Fn::Sub intrinsic function

        Parameters
        ----------
        data
            Data to check

        Returns
        -------
        bool
            True if the data Fn::Sub intrinsic function

def _is_sub_intrinsic(data):
        """
        Is this input data a Fn::Sub intrinsic function

        Parameters
        ----------
        data
            Data to check

        Returns
        -------
        bool
            True if the data Fn::Sub intrinsic function
        """
        return isinstance(data, dict) and len(data) == 1 and LambdaUri._FN_SUB in data