:param format_type: The format need to output.
        :return: formatted output.
        :raise ConversionError: data can't be converted to the specified format_type.

def get_formatted_output(self, format_type=FormatType.JSON):
        """
        :param format_type: The format need to output.
        :return: formatted output.
        :raise ConversionError: data can't be converted to the specified format_type.
        """
        if format_type not in [FormatType.JSON, FormatType.YAML]:
            raise ArgumentInvalid('"format_type" should be one of FormatType.JSON / YAML!')
        elif format_type is FormatType.JSON:
            return self._format_json()
        elif format_type is FormatType.YAML:
            return self._format_yaml()