code: def test_add_scalar(self):
      x = range(100)
      for i in x:
          summary.add_scalar("y_2x", i * 2, i)
      self.assertTrue(os.path.exists("./train_log/summary_test"))
  
file_path: PARL/parl/utils/tests/summary_test.py
imports: import unittest
  from parl.utils import summary
  import numpy
  from parl.utils import logger
  import os
label_desc: Use image node_id 2 for calling the TestUtils obj's underlying member method code with example usage: obj.test_add_scalar() without return types