def requires_conversion(cls, fileset, file_format):
        """Checks whether the fileset matches the requested file format"""
        if file_format is None:
            return False
        try:
            filset_format = fileset.format
        except AttributeError:
            return False  # Field input
        else:
            return (file_format != filset_format)
Checks whether the fileset matches the requested file format