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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_used_fields(payload):
 """ Get a list containing the names of the fields that are used in the xso.Query. :param payload: Query object o be :type payload: :class:`~aioxmpp.ibr.Query` :return: :attr:`list` """

    return [
        tag
        for tag, descriptor in payload.CHILD_MAP.items()
        if descriptor.__get__(payload, type(payload)) is not None
    ]