title: How tf.contrib.seq2seq.TrainingHelper can be replaced in TensorFlow 2.2
body: <p>I am trying to run the project from <a href="https://github.com/kunalBhashkar/tensorflow_spelling_correction" rel="nofollow noreferrer">GitHub</a> but I have a trouble with TrainingHelper. Now, I am stuck with it, I dont know how to convert it to tf2. The console always returns the error like this:</p>
  <pre><code>AttributeError: module 'tensorflow_addons.seq2seq' has no attribute 'TrainingHelper'
  </code></pre>
  <p>Please help me!</p>