code: def _call_command(self, name, *args, **kwargs):
          
          obj = getattr(self, '_instance', self)  # _instance if a field, self if an instance
  
          # The object may not be already connected, so if we want to update a
          # field, connect it before.
          # If the object as no PK yet, let the object create itself
          if name in self.available_modifiers and obj._pk and not obj.connected:
              obj.connect()
  
          # Give priority to a "_call_{commmand}" method
          meth = getattr(self, '_call_%s' % name, self._traverse_command)
          return meth(name, *args, **kwargs)
docs: Check if the command to be executed is a modifier, to connect the object.
          Then call _traverse_command.