Recursively resolves "Fn::FindInMap"references that are present in the mappings and returns the value.
        If it is not in mappings, this method simply returns the input unchanged.

        :param input_dict: Dictionary representing the FindInMap function. Must contain only one key and it
                           should be "Fn::FindInMap".

        :param parameters: Dictionary of mappings from the SAM template

def resolve_parameter_refs(self, input_dict, parameters):
        """
        Recursively resolves "Fn::FindInMap"references that are present in the mappings and returns the value.
        If it is not in mappings, this method simply returns the input unchanged.

        :param input_dict: Dictionary representing the FindInMap function. Must contain only one key and it
                           should be "Fn::FindInMap".

        :param parameters: Dictionary of mappings from the SAM template
        """
        if not self.can_handle(input_dict):
            return input_dict

        value = input_dict[self.intrinsic_name]

        # FindInMap expects an array with 3 values
        if not isinstance(value, list) or len(value) != 3:
            raise InvalidDocumentException(
                [InvalidTemplateException('Invalid FindInMap value {}. FindInMap expects an array with 3 values.'
                                          .format(value))])

        map_name = self.resolve_parameter_refs(value[0], parameters)
        top_level_key = self.resolve_parameter_refs(value[1], parameters)
        second_level_key = self.resolve_parameter_refs(value[2], parameters)

        if not isinstance(map_name, string_types) or \
                not isinstance(top_level_key, string_types) or \
                not isinstance(second_level_key, string_types):
            return input_dict

        if map_name not in parameters or \
                top_level_key not in parameters[map_name] or \
                second_level_key not in parameters[map_name][top_level_key]:
            return input_dict

        return parameters[map_name][top_level_key][second_level_key]