code: def has_item(self, item_url):
          
          c = self.conn.cursor()
          c.execute("SELECT * FROM items WHERE url=?", (str(item_url),))
          row = c.fetchone()
          c.close()
          return self.__exists_row_not_too_old(row)
docs: Check if the metadata for the given item is present in
          the cache
  
          If the max_age attribute of this Cache is set to a nonzero value,
          entries older than the value of max_age in seconds will be ignored
  
          :type item_url: String or Item
          :param item_url: the URL of the item, or an Item object
  
          :rtype: Boolean
          :returns: True if the item is present, False otherwise