code: def find_obj_by_tag(self, tag):
          
          for obj in self.__up_objects:
              if obj.tag == tag:
                  return obj
  
          for obj in self.__draw_objects:
              if obj.tag == tag:
                  return obj
  
          return None
docs: Search through all the objects in the world and
          return the first instance whose tag matches the specified string.