title: Tensor.graph is meaningless when eager execution is enabled
body: <pre><code>a = tf.compat.v1.constant(5.0)
  b = tf.compat.v1.constant(6.0)
  
  sum1 = a + b
  g = tf.compat.v1.Graph()
  with g.as_default():
      # Define operations and tensors in `g`.
      hello = tf.compat.v1.constant('hello')
      assert hello.graph is g
  
  sess = tf.compat.v1.Session(graph=g)
  
  print(sess.run(sum1))
  
  
  </code></pre>
  
  <p>tensorflow-gpu2.0
  i don't know why. i am a beginner of tensorflow</p>