<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def query_band(self, value):
 """Set the connection's query_band property. Args: value: New query_band value. String. Returns: Nothing. """


        self._query_band = value
        # If query band is None we remove the element and don't write it to XML
        if value is None:
            try:
                del self._connectionXML.attrib['query-band-spec']
            except KeyError:
                pass
        else:
            self._connectionXML.set('query-band-spec', value)