def METHOD_NAME(self, box, n=10):
    qmesh = rectangledomainmesh(box, nx=n, ny=n, meshtype='quad')
    node = qmesh.entity('node')
    cell = qmesh.entity('cell')
    NC = qmesh.number_of_cells()
    isLeftCell = np.zeros((n, n), dtype=np.bool_)
    isLeftCell[0::2, :] = True
    isLeftCell = isLeftCell.reshape(-1)
    lcell = cell[isLeftCell]
    rcell = cell[~isLeftCell]
    newCell = np.r_['0', 
            lcell[:, [1, 2, 0]], 
            lcell[:, [3, 0, 2]],
            rcell[:, [0, 1, 3]],
            rcell[:, [2, 3, 1]]]
    return TriangleMesh(node, newCell)
    #cross mesh