code: def FB(circuit, *, out_port=None, in_port=None):
      
      if out_port is None:
          out_port = circuit.cdim - 1
      if in_port is None:
          in_port = circuit.cdim - 1
      return Feedback.create(circuit, out_port=out_port, in_port=in_port)
docs: Wrapper for :class:`.Feedback`, defaulting to last channel
  
      Args:
          circuit (Circuit): The circuit that undergoes self-feedback
          out_port (int): The output port index, default = None --> last port
          in_port (int): The input port index, default = None --> last port
  
      Returns:
          Circuit: The circuit with applied feedback operation.