code: def position(self, pos=None):
  		
  		if pos is not None:
  			if pos >= len(self.__history):
  				raise IndexError('History position is out of bound')
  			self.__history_position = pos
  		return self.__history_position
docs: Get current and/or set history cursor position
  
  		:param pos: if value is not None, then current position is set to pos and new value is returned
  
  		:return: int or None (if position have never been changed)