code: def test_ngd_step_groups(self):
      parameters = [
          {
              "params": [torch.nn.Parameter(torch.tensor(2.5))],
              "lr": 0.2,
          },
          {"params": [torch.nn.Parameter(torch.tensor([1.0, -0.5]))]},
      ]
  
      optimizer = NGD(parameters, num_data=5, lr=0.1)
      optimizer.zero_grad()
      loss = parameters[0]["params"][0] + torch.dot(
          parameters[1]["params"][0], torch.tensor([2.0, -1])
      )
      loss.backward()
      optimizer.step()
  
      self.assertAllClose(parameters[0]["params"][0], torch.tensor(1.5))
      self.assertAllClose(
          parameters[1]["params"][0], torch.tensor([0.0, 0.0])
      )
  
file_path: gpytorch/test/optim/test_ngd.py
imports: import unittest
  import torch
  from gpytorch.optim import NGD
  from gpytorch.test.base_test_case import BaseTestCase
label_desc: Use image node_id 2 for calling the TestNGD obj's underlying member method code with example usage: obj.test_ngd_step_groups() without return types