def trim_exams(image_channels):
    """
    Trims the larger exam to match length.

    Receives arbitrary list of (num_frames, height, width) as input. The number
    of frames between the exams will be trimmed to match the dimensionality
    of the smallest exams.
    """
    min_frames = min([channel.shape[0] for channel in image_channels])
    return [channel[:min_frames] for channel in image_channels]