def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def encode(self):
        return {
            'af': ip_address(self.gaddr).vapi_af,
            'grp_address': {
                ip_address(self.gaddr).vapi_af_name: self.gaddr
            },
            'src_address': {
                ip_address(self.saddr).vapi_af_name: self.saddr
            },
            'grp_address_length': self.glen,
        }