code: def test_latency_improvement_rate__optimized_latency_is_zero(self):
      original_latency = 1.0
      optimized_latency = 0.0
      res = OptimizeInferenceResult(
          original_model=MagicMock(latency_seconds=original_latency),
          hardware_setup=MagicMock(),
          optimized_model=MagicMock(latency_seconds=optimized_latency),
      )
      self.assertEqual(-1, res.latency_improvement_rate)
  
imports: import unittest
  from unittest.mock import MagicMock
  from nebullvm.core.models import OptimizeInferenceResult
label_desc: Use image node_id 2 for calling the TestOptimizeInferenceResult obj's underlying member method code with example usage: obj.test_latency_improvement_rate__optimized_latency_is_zero() without return types