def is_static_XX_field(field_id, cubes_lookup):
    """
    GA has fields that are documented using a placeholder of `XX`, where
    the `XX` is replaced with a number in practice.

    Some of these are standard fields with constant numeric
    representations. These must be handled differently from other field,
    so this function will detect this case using the information we have
    gleaned in our cubes_lookup values.

    If the cubes_lookup map does NOT have the `XX` version in it, this
    function assumes that it has only the numeric versions.
    """
    return ('XX' in field_id and field_id not in cubes_lookup and field_id
         not in ['ga:metricXX', 'ga:dimensionXX'])
