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 __init__(self, key):
        self.key = key
        self.prio = random.randint(0, 1000000000)
        self.size = 1
        self.left = None
        self.right = None