def __str__(self):
        return "".join([self.package, self.version or ""])
def __init__(self, directory=None):
        if directory is None:
                directory = []
        import copy
        self.directory = copy.deepcopy(directory)
        self.bound = False
        self.start_tls_called = False
        self.extend = self.Extend(self)

        self.operation = {
                    "!" : self._search_not,
                    "&" : self._search_and,
                    "|" : self._search_or,
            }