def METHOD_NAME(self, signature):
    url = makeurl(self.apiurl, ['source', self.lock, '_attribute'])
    data = """
    <attributes>
      <attribute namespace='%s' name='LockedBy'>
        <value>%s</value>
      </attribute>
    </attributes>""" % (self.ns, signature)
    http_POST(url, data=data)