def remove_writer(socket)
      if event_mask_for_socket(socket) == ZMQ::POLLOUT
        remove(socket)
        return
      end
      raise ArgumentError, "not registered for writability only: %p" % socket
    end
def remove_writer(socket)
      if event_mask_for_socket(socket) == ZMQ::POLLOUT
        remove(socket)
        return
      end
      raise ArgumentError, "not registered for writability only: %p" % socket
    end
Removes a reader socket that was registered for writability only.

 @param socket [Socket, Actor] the socket
 @raise [ArgumentError] if it's not registered, not registered for
   writability, or registered for more than just writability