docs: def _get_binding_keys(self, port, host):
          """Get binding keys from the port binding"""
          binding_keys = list()
          switch_binding = port[portbindings.PROFILE].get(
              'local_link_information', None)
          if switch_binding:
              for binding in switch_binding:
                  switch_id = binding.get('switch_id')
                  port_id = binding.get('port_id')
                  binding_keys.append((port['id'], (switch_id, port_id)))
          else:
              binding_keys.append((port['id'], host))
          return binding_keys