code: def test_step_scheduler(self):
      gamma = 0.1
      step_size = 2
      scheduler = StepGradClip(
          self.optimizer, step_size=step_size, gamma=gamma
      )
  
      self.assertEqual(self.optimizer.max_grad_norm, 1.0)
      scheduler.step()
      self.assertEqual(self.optimizer.max_grad_norm, 1.0)
      scheduler.step()
      self.assertEqual(self.optimizer.max_grad_norm, gamma)
      scheduler.step()
      self.assertEqual(self.optimizer.max_grad_norm, gamma)
      scheduler.step()
      self.assertEqual(self.optimizer.max_grad_norm, gamma**2)
  
file_path: opacus/opacus/tests/schedulers/grad_clip_scheduler_test.py
imports: import unittest
  import torch
  from opacus import PrivacyEngine
  from opacus.schedulers import ExponentialGradClip, LambdaGradClip, StepGradClip
  from torch import nn, optim
  from torch.utils.data import DataLoader, TensorDataset
label_desc: Use image node_id 3 for calling the GradClipSchedulerTest obj's underlying member method code with example usage: obj.test_step_scheduler() without return types