code: def value(self):
      
      if not self.filled:
        raise SlotNotFilledError('Slot with name "%s", key "%s" not yet filled.'
                                 % (self.name, self.key))
      return self._value
docs: Returns the current value of this slot.
  
      Returns:
        The value of the slot (a serializable Python type).
  
      Raises:
        SlotNotFilledError if the value hasn't been filled yet.