code: def _getter(self, obj):
          
          result = None
  
          if self._fget_ is not None:
              result = self._fget_(obj)
  
          if result is None:
              result = getattr(obj, self._attrname(), self._default_)
  
          # notify parent schema about returned value
          if isinstance(obj, Schema):
              obj._getvalue(self, result)
  
          return result
docs: Called when the parent element tries to get this property value.
  
          :param obj: parent object.