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 update(self, *args, **kwargs):
        chain = []
        for arg in args:
            if isinstance(arg, dict):
                iterator = arg.items()
            else:
                iterator = arg
            chain = itertools.chain(chain, iterator)
        if kwargs:
            chain = itertools.chain(chain, kwargs.items())
        for key, value in iterator:
            self._collection[key] = self._from_python(key, value)