@staticmethod
def __determine_mask_mode(mask_string: str):
    """If the mask string starts with '0:' or '1:', or generally
        if it contains a non-0 or 1 symbol, assume it is RLE."""
    mode = 'bitmap'
    if len(mask_string) < 3:
        mode = 'bitmap'
    elif ':' in mask_string[:3]:
        mode = 'rle'
    return mode
