def split_channel(tensor, split_type='simple'):
    """
    Split channels of tensor

    :param tensor: input tensor
    :type tensor: torch.Tensor
    :param split_type: type of splitting
    :type split_type: str
    :return: split tensor
    :rtype: tuple(torch.Tensor, torch.Tensor)
    """
    assert len(tensor.shape) == 4
    assert split_type in ['simple', 'cross']

    nc = tensor.shape[1]
    if split_type == 'simple':
        return tensor[:, :nc // 2, ...], tensor[:, nc // 2:, ...]
    elif split_type == 'cross':
        return tensor[:, 0::2, ...], tensor[:, 1::2, ...]