def inside_poly(points, verts):
    """
    *points* is a sequence of *x*, *y* points.
    *verts* is a sequence of *x*, *y* vertices of a polygon.

    Return value is a sequence of indices into points for the points
    that are inside the polygon.
    """
    res, =  np.nonzero(nxutils.points_inside_poly(points, verts))
    return res