code: def link(self, to):
      
      self._assert_bound()
      self._context.link(self.pid, to)
docs: Link to another process.
  
      The ``link`` operation is not guaranteed to succeed.  If it does, when
      the other process terminates, the ``exited`` method will be called with
      its pid.
  
      Returns immediately.
  
      :param to: The pid of the process to send a message.
      :type to: :class:`PID`
      :raises: Will raise a ``Process.UnboundProcess`` exception if the
               process is not bound to a context.
      :return: Nothing