<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_hgnc_entry(hgnc_id):
 """Return the HGNC entry for the given HGNC ID from the web service. Parameters hgnc_id : str The HGNC ID to be converted. Returns ------- xml_tree : ElementTree The XML ElementTree corresponding to the entry for the given HGNC ID. """

    url = hgnc_url + 'hgnc_id/%s' % hgnc_id
    headers = {'Accept': '*/*'}
    res = requests.get(url, headers=headers)
    if not res.status_code == 200:
        return None
    xml_tree = ET.XML(res.content, parser=UTB())
    return xml_tree