What is the purpose of the tf.contrib module in Tensorflow?
<p>I'm curious about what <code>tf.contrib</code> is, and why the code would be included in TensorFlow, but not in the main repository.</p>

<p>Furthermore, looking at the example <a href="https://github.com/tensorflow/tensorflow/blob/master/tensorflow/examples/learn/wide_n_deep_tutorial.py" rel="noreferrer">here</a> (from the tensorflow master branch), and I want to find the source for <code>tf.contrib.layers.sparse_column_with_hash_bucket</code>. </p>

<p>It seems like some cool routines, but I wanted to make sure they were properly using queues, etc, for pre-fetching/pre-processing examples to actually use them in a production setting. </p>

<p>It appears to be documented <a href="https://www.tensorflow.org/versions/r0.9/api_docs/python/contrib.learn.html#TensorFlowClassifier" rel="noreferrer">here</a>, but it is from the <a href="https://github.com/tflearn" rel="noreferrer">tflearn</a> project, but <code>tf.contrib.layers.sparse_column_with_hash_bucket</code> doesn't seem to be in that repository either.</p>