Remove reference from self to ref

        >>> iip = Resource('instance-ip',
                           uuid='30213cf9-4b03-4afc-b8f9-c9971a216978',
                           fetch=True)
        >>> for vmi in iip['virtual_machine_interface_refs']:
                iip.remove_ref(vmi)
        >>> iip['virtual_machine_interface_refs']
        KeyError: u'virtual_machine_interface_refs'

        :param ref: reference to remove
        :type ref: Resource

        :rtype: Resource

def remove_ref(self, ref):
        """Remove reference from self to ref

        >>> iip = Resource('instance-ip',
                           uuid='30213cf9-4b03-4afc-b8f9-c9971a216978',
                           fetch=True)
        >>> for vmi in iip['virtual_machine_interface_refs']:
                iip.remove_ref(vmi)
        >>> iip['virtual_machine_interface_refs']
        KeyError: u'virtual_machine_interface_refs'

        :param ref: reference to remove
        :type ref: Resource

        :rtype: Resource
        """
        self.session.remove_ref(self, ref)
        return self.fetch()