code: def get_item_type(self, ttype):
          
          for i in self.map_item:
              if TYPE_MAP_ITEM[i.get_type()] == ttype:
                  return i.get_item()
          return None
docs: Get a particular item type
  
              :param ttype: a string which represents the desired type
  
              :rtype: None or the item object