title: TF 2.0: how to convert 'tf.contrib.eager.num_gpus()'?
body: <p>I found no way to get a 'num_gpus' function working in TF 2.0.
  Thought it should be somehow possible with 'compat.v1'.</p>
  
  <p>I used 'tensorflow.contrib.eager.num_gpus()' within a helper_function to initialize gpu if present.</p>
  
  <p>What is the intended way to get the desired info in TF 2.0?</p>