code: def reload(self, d=None):
          
          if d:
              self.clear()
              self.update(d)
          elif self.id:
              new_dict = self.by_id(self._id)
              self.clear()
              self.update(new_dict)
          else:
              # should I raise an exception here?
              # Like "Model must be saved first."
              pass
docs: Reload model from given dict or database.