title: How to map a function with additional parameter using the new Dataset api in TF1.3?
body: <p>I'm playing with <a href="https://www.tensorflow.org/programmers_guide/datasets" rel="noreferrer">the Dataset API in Tensorflow v1.3</a>. It's great.
  It is possible to map a dataset with a function as described <a href="https://www.tensorflow.org/programmers_guide/datasets#preprocessing_data_with_datasetmap" rel="noreferrer">here</a>. I am interested to know how can I pass a function which has an additional argument, for example <code>arg1</code>:</p>
  
  <pre><code>def _parse_function(example_proto, arg1):
    features = {"image": tf.FixedLenFeature((), tf.string, default_value=""),
                "label": tf.FixedLenFeature((), tf.int32, default_value=0)}
    parsed_features = tf.parse_single_example(example_proto, features)
    return parsed_features["image"], parsed_features["label"]
  </code></pre>
  
  <p>Of course,</p>
  
  <pre><code>dataset = dataset.map(_parse_function)
  </code></pre>
  
  <p>will not work since there is no way to pass in <code>arg1</code>.</p>