def METHOD_NAME(self) -> Polygon:
    """Returns a single polygon for the entire zoning coverage
    :Returns:
        **model coverage** (:obj:`Polygon`): Shapely (Multi)polygon of the zoning system.
    """
    self._curr.execute('Select ST_asBinary("geometry") from zones;')
    polygons = [shapely.wkb.loads(x[0]) for x in self._curr.fetchall()]
    return unary_union(polygons)