def extract_multi_polygon(feature):
    """
    Extracts the coordinates of a GeoJSON Feature of either type Polygon or Multipolygon,
    implicitly converting the coordinates to the form of a Multipolygon.
    """
    kind = feature["geometry"]["type"]
    if kind == "Polygon":
        return [feature["geometry"]["coordinates"]]
    elif kind == "MultiPolygon":
        return feature["geometry"]["coordinates"]
    else:
        raise ValueError("Feature has wrong type: {}".format(kind))