def __get_shift__(match):
    """
    Parses the shift part of a filename e.g. +128, -110
    """
    shift = 0
    keys = match.groupdict().keys()
    if "operator" in keys and "shift_si" in keys:
        operator = match.group('operator')
        shift_str = match.group('shift')
        if operator != '' and shift_str:
            shift = int(shift_str)
            if operator == "-":
                shift = -shift
    return shift