code: def testGradientAtZero(self):
      with self.cached_session():
          logits = constant_op.constant(
              [0.0, 0.0], dtype=dtypes.float64
          )
          targets = constant_op.constant(
              [0.0, 1.0], dtype=dtypes.float64
          )
          loss = nn_impl.sigmoid_cross_entropy_with_logits(
              labels=targets, logits=logits
          )
          grads = gradients_impl.gradients(loss, logits)[0].eval()
      self.assertAllClose(grads, [0.5, -0.5])
  
imports: import math
  import numpy
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import gradient_checker
  from tensorflow.python.ops import gradients_impl
  from tensorflow.python.ops import nn_impl
  import tensorflow.python.ops.nn_grad
  from tensorflow.python.platform import test
label_desc: Use image node_id 7 for calling the SigmoidCrossEntropyWithLogitsTest obj's underlying member method code with example usage: obj.testGradientAtZero() without return types