def __init__(self, package, version):
        """Construct a new requirement.

        :param package: the package name.
        :param version: a semver compatible version specification.
        """
        self.package = package
        self.version = version
        if self.version and not re.match(r"[<=>~]", version[:2]):
            self.version = "=={}".format(self.version)
def _exit_modes_beyond(self, thisMode):
        if not self.modeList: return
        while len(self.modeList) > thisMode + 1: 
            self.modeList.pop().exit()