code: def disconnect(self):
      self.__connection.close()
      self.__connection = None
  
imports: from pyalgotrade.barfeed import dbfeed
  from pyalgotrade.barfeed import membf
  from pyalgotrade import bar
  from pyalgotrade.utils import dt
  import sqlite3
  import os
label_desc: Use image node_id 8 for calling the Database obj's underlying member method code with example usage: obj.disconnect() without return types