def pts_in_cell_numpy(pts, cell):
    """ get the point indices incide of a given cell (numpy)
    Input: 
        pts,        a set of points in numpy format
        cell,       a list of 6 numbers {x1, y1, z1, x2, y2, z2}
    Output:
        inds,       a list of indices for points inside the cell
    """
    N = pts.shape[0] 
    inds = [i for i in range(N) if pts[i,0]>cell[0] and pts[i,0] < cell[3] 
                               and pts[i,1]>cell[1] and pts[i,1] < cell[4] 
                               and pts[i,2]>cell[2] and pts[i,2] < cell[5]] 
    return inds