title: tf.data.Dataset from tf.keras.preprocessing.image.ImageDataGenerator.flow_from_directory?
body: <p>How do I create a <a href="https://www.tensorflow.org/api_docs/python/tf/data/Dataset" rel="noreferrer"><code>tf.data.Dataset</code></a> from <a href="https://www.tensorflow.org/versions/r1.8/api_docs/python/tf/keras/preprocessing/image/ImageDataGenerator#flow_from_directory" rel="noreferrer"><code>tf.keras.preprocessing.image.ImageDataGenerator.flow_from_directory</code></a>?</p>
  
  <p>I'm considering <a href="https://www.tensorflow.org/api_docs/python/tf/data/Dataset#from_generator" rel="noreferrer"><code>tf.data.Dataset.from_generator</code></a>, but it's unclear how to acquire the <code>output_types</code> keyword argument for it, given the return type:</p>
  
  <blockquote>
    <p>A <code>DirectoryIterator</code> yielding tuples of <code>(x, y)</code> where <code>x</code> is a numpy array containing a batch of images with shape <code>(batch_size, *target_size, channels)</code> and <code>y</code> is a numpy array of corresponding labels.</p>
  </blockquote>