How to use the depccg.fixed_length_n_step_lstm.PointerArray function in depccg

def _make_tensor_descriptor_array(xs, length):
    """Make an array of pointers denoting pointers of tensor descriptors.

    """
    descs = []
    batch_size = xs.shape[0] // length
    for i in range(length):
        x = xs[i*batch_size:(i+1)*batch_size]
        if x.ndim < 3:
            shape = x.shape + (1,) * (3 - x.ndim)
            x = x.reshape(shape)
        desc = cudnn.create_tensor_nd_descriptor(x)
        descs.append(desc)
    return PointerArray([d.value for d in descs], descs)