def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def query_vpp_config(self):
        ds = list(self._test.vapi.vpp.details_iter(
            self._test.vapi.ip_path_mtu_get))

        for d in ds:
            if self.nh == str(d.pmtu.nh) \
               and self.table_id == d.pmtu.table_id \
               and self.pmtu == d.pmtu.path_mtu:
                return True
        return False