Perform many-to-many files conversion.
        :return: None
        :rtype: :py:obj:`None`

def _many_to_many(self):
        """Perform many-to-many files conversion.
        :return: None
        :rtype: :py:obj:`None`
        """
        if not self.file_generator.to_path_compression:
            self._to_dir(self.file_generator)
        elif self.file_generator.to_path_compression == "zip":
            self._to_zipfile(self.file_generator)
        elif self.file_generator.to_path_compression in ("tar", "tar.gz", "tar.bz2"):
            self._to_tarfile(self.file_generator)
        elif self.file_generator.to_path_compression in ("gz", "bz2"):
            raise TypeError('Many-to-one conversion, cannot convert "{}" into "{}"'.format(self.file_generator.from_path,
                                                                                           self.file_generator.to_path))
        else:
            raise TypeError('Unknown output file format: "{}"'.format(self.file_generator.to_path))