code: def set_real_value_class(self):
          
          if self.value_class is not None and isinstance(self.value_class, str):
              module_name, dot, class_name = self.value_class.rpartition(".")
              module = __import__(module_name, fromlist=[class_name])
              self.value_class = getattr(module, class_name)
              self._initialized = True
docs: value_class is initially a string with the import path to the resource class, but we need to get the actual class before doing any work
  
          We do not expect the actual clas to be in value_class since the beginning to avoid nasty import egg-before-chicken errors