def register_new_peak(background_index_left, background_index_right, keys):
    """Registers a new peak by creating a peak from the background values given

    Args:
        background_index_left (int): index in compressed depths of background left to a peak
        background_index_right (int): index in compressed depths of background right to a peak
        keys (List): The keys for the compressed depths dictionary

    Returns:
        str: A peak in start - end format that is the result of registration
    """
    if background_index_right - background_index_left >= 5:
        peak = keys[background_index_left + 1][0], keys[background_index_right - 1][1]
    else:
        peak = keys[background_index_left][0], keys[background_index_right][1]

    return peak