title: What is tensorflow.python.data.ops.dataset_ops._OptionsDataset?
body: <p>I am using the Transformer code from tensorflow - <a href="https://www.tensorflow.org/beta/tutorials/text/transformer" rel="noreferrer">https://www.tensorflow.org/beta/tutorials/text/transformer</a></p>
  
  <p>In this code, the dataset used is loaded like this - </p>
  
  <pre><code>examples, metadata = tfds.load('ted_hrlr_translate/pt_to_en', with_info=True,
                                 as_supervised=True)
  train_examples, val_examples = examples['train'], examples['validation']
  </code></pre>
  
  <p>When I check the type of train_examples using :</p>
  
  <pre><code>type(train_examples)
  </code></pre>
  
  <p>I get the following as output - </p>
  
  <pre><code>tensorflow.python.data.ops.dataset_ops._OptionsDataset
  </code></pre>
  
  <p>Now I just wanted to change some entries of the dataset that is the sentences, but I am not able to as I don't understand the type.</p>
  
  <p>I am able to iterate over it using :</p>
  
  <pre><code>for data in train_examples:
      print(data,type(data))
  </code></pre>
  
  <p>And type of data is - </p>
  
  <pre><code>&lt;class 'tuple'&gt;
  </code></pre>
  
  <p>Finally what I want is to replace some of these tuples with my own data.
  Can someone tell me how to do this or give me some details about this type 
  <code>tensorflow.python.data.ops.dataset_ops._OptionsDataset</code>.</p>