def _coords(shape):
    """
    Return a list of lists of coordinates of the polygon. The list consists
    firstly of the list of exterior coordinates followed by zero or more lists
    of any interior coordinates.
    """

    assert shape.geom_type == 'Polygon'
    coords = [list(shape.exterior.coords)]
    for interior in shape.interiors:
        coords.append(list(interior.coords))
    return coords