title: ModuleNotFoundError: No module named 'tensorflow.contrib' when from tensorflow.contrib.seq2seq import Helper is used
body: <p>The title may be similar to other posts, but what I ask here is specific and not yet answered by anyone. So I need your help</p>
  <p>I get the following error
  <code>ModuleNotFoundError: No module named 'tensorflow.contrib</code>
  when I try</p>
  <p><code>from tensorflow.contrib.seq2seq import Helper</code></p>
  <p>I've installed tensorflow-addons.
  <code>from tensorflow_addons.seq2seq import Helper</code> is not working either</p>
  <p><strong>I need to import Helper from seq2seq</strong></p>
  <p>What should I do?</p>
  <p>My tensorflow version is 2.2.0</p>
  <p>My tensorflow-addons version is 0.11.2</p>