code: def get_primary_text(self, item_url):
          
          c = self.conn.cursor()
          c.execute("SELECT * FROM primary_texts WHERE item_url=?",
                        (str(item_url),))
          row = c.fetchone()
          c.close()
          if row is None:
              raise ValueError("Item not present in cache")
          return row[1]
docs: Retrieve the primary text for the given item from the cache.
  
          :type item_url: String or Item
          :param item_url: the URL of the item, or an Item object
  
          :rtype: String
          :returns: the primary text
  
          :raises: ValueError if the primary text is not in the cache