def get_gaf_gene_ontology_file(path):
assert isinstance(path, str)<EOL>version = None<EOL>with misc.smart_open_read(path, encoding='<STR_LIT>', try_gzip=True) as fh:<EOL><INDENT>for l in fh:<EOL><INDENT>if l[<NUM_LIT:0>] != '<STR_LIT:!>':<EOL><INDENT>break<EOL><DEDENT>if l.startswith('<STR_LIT>'):<EOL><INDENT>version = l.split('<STR_LIT:U+0020>')[<NUM_LIT:1>]<EOL>break<EOL><DEDENT><DEDENT><DEDENT>return version<EOL>
Extract the gene ontology file associated with a GO annotation file.

    Parameters
    ----------
    path: str
        The path name of the GO annotation file.

    Returns
    -------
    str
        The URL of the associated gene ontology file.