code: def test_ranker(self):
      testing_utils.train_model(
          {
              "task": "integration_tests",
              "model": "transformer/ranker",
              "candidates": "batch",
              "data_parallel": True,
              **MODEL_OPTS,
          }
      )
  
file_path: ParlAI/tests/test_multigpu.py
imports: import unittest
  import parlai.utils.testing
label_desc: Use image node_id 2 for calling the TestDataParallel obj's underlying member method code with example usage: obj.test_ranker() without return types