code: def add(self, recv):
          
          if isinstance(recv, Select):
              recv._check_no_loop(self)
  
          self._receivers.append(recv)
          if recv.notify is not None:
              raise Error(self.owned_msg)
  
          recv.notify = self._put
          # Avoid race by polling once after installation.
          if not recv.empty():
              self._put(recv)
docs: Add a :class:`mitogen.core.Receiver`, :class:`Select` or
          :class:`mitogen.core.Latch` to the select.
  
          :raises mitogen.select.Error:
              An attempt was made to add a :class:`Select` to which this select
              is indirectly a member of.