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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_gaf_gene_ontology_file(path):
 """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. """

    assert isinstance(path, str)

    version = None
    with misc.smart_open_read(path, encoding='UTF-8', try_gzip=True) as fh:
        for l in fh:
            if l[0] != '!':
                break
            if l.startswith('!GO-version:'):
                version = l.split(' ')[1]
                break
    return version