def skip_regex(lines_enum, options):
    # type: (ReqFileLines, Optional[optparse.Values]) -> ReqFileLines
    """
    Skip lines that match '--skip-requirements-regex' pattern

    Note: the regex pattern is only built once
    """
    skip_regex = options.skip_requirements_regex if options else None
    if skip_regex:
        pattern = re.compile(skip_regex)
        lines_enum = filterfalse(lambda e: pattern.search(e[1]), lines_enum)
    return lines_enum