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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 uniprot_sites(uniprot_id):
 """Retrieve a list of UniProt sites parsed from the feature file Sites are defined here: http://www.uniprot.org/help/site and here: http://www.uniprot.org/help/function_section Args: uniprot_id: Valid UniProt ID Returns: """


    r = requests.post('http://www.uniprot.org/uniprot/%s.gff' % uniprot_id)
    gff = StringIO(r.content.decode('utf-8'))

    feats = list(GFF.parse(gff))
    if len(feats) > 1:
        log.warning('Too many sequences in GFF')
    else:
        return feats[0].features