code: def test_natural_gradient(self):
      self.start_tests(name="natural-gradient")
  
      self.unittest(
          optimizer=dict(
              type="natural_gradient",
              learning_rate=1e-3,
              only_positive_updates=False,
          )
      )
  
file_path: tensorforce/test/test_optimizers.py
imports: import unittest
  from test.unittest_base import UnittestBase
label_desc: Use image node_id 3 for calling the TestOptimizers obj's underlying member method code with example usage: obj.test_natural_gradient() without return types