code: def test_output_str(self):
      self.assertTrue(isinstance(query_memory(2), str))
      all_device = query_memory(-1)
      self.assertTrue(isinstance(all_device, str))
      self.assertEqual(query_memory("test"), "")
  
imports: from __future__ import annotations
  import unittest
  from tests.utils import query_memory
label_desc: Use image node_id 1 for calling the TestQueryMemory obj's underlying member method code with example usage: obj.test_output_str() without return types