def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def __init__(self, test, rx_index, tx_index, nh_addr):
        self._test = test
        self._rx_index = rx_index
        self._tx_index = tx_index
        self._nh_addr = ip_address(nh_addr)