code: def machine_op(self, operation):
          '''Perform machine operations
          
          Args:
              operations: which operation you would like
          Returns:
              None
          Raises:
              RuntimeError: Invalid operation
          '''
          operations = {'feed2start': 1,
                        'feedone': 2,
                        'cut': 3
                        }
          
          if operation in operations:
              self.send('^'+'O'+'P'+chr(operations[operation]))
          else:
              raise RuntimeError('Invalid operation.'f machine_op(self, operation):
          '''Perform machine operations
          
          Args:
              operations: which operation you would like
          Returns:
              None
          Raises:
              RuntimeError: Invalid operation
          '''
          operations = {'feed2start': 1,
                        'feedone': 2,
                        'cut': 3
                        }
          
          if operation in operations:
              self.send('^'+'O'+'P'+chr(operations[operation]))
          else:
              raise RuntimeError('Invalid operation.')
docs: Perform machine operations
          
          Args:
              operations: which operation you would like
          Returns:
              None
          Raises:
              RuntimeError: Invalid operation