code: def test_zero_valid_entries(self):
      m_obj = metrics.MeanIoU(num_classes=2)
      self.assertAllClose(m_obj.result(), 0, atol=1e-3)
  
imports: import numpy
  import pytest
  from keras import layers
  from keras import models
  from keras import testing
  from keras.metrics import iou_metrics
label_desc: Use image node_id 8 for calling the MeanIoUTest obj's underlying member method code with example usage: obj.test_zero_valid_entries() without return types