code: def test_async_subclass(self):
      class MyConn(ext.connection):
          def __init__(self, dsn, async_=0):
              ext.connection.__init__(self, dsn, async_=async_)
  
      conn = self.connect(connection_factory=MyConn, async_=True)
      self.assert_(isinstance(conn, MyConn))
      self.assert_(conn.async_)
      conn.close()
  
imports: import gc
  import time
  import unittest
  import warnings
  import psycopg2
  import psycopg2.errors
  from psycopg2 import extensions
  from .testutils import ConnectingTestCase, StringIO, skip_before_postgres, skip_if_crdb, crdb_version, slow
label_desc: Use image node_id 19 for calling the AsyncTests obj's underlying member method code with example usage: obj.test_async_subclass() without return types