def image_channel(I, channel):
    """
    Extracts the specified channel(s) from the input Neural Renderer image

    Parameters
    ----------
    I : Tensor
        the Neural Renderer image
    channel : int or list of ints
        the channel(s) to extract

    Returns
    -------
    Tensor
        the selected channel(s)
    """

    return I[:, channel, :, :]