title: What is a nested structure in TensorFlow?
body: <p>Going over the documentation for <a href="https://www.tensorflow.org/api_docs/python/tf/data/Dataset" rel="nofollow noreferrer">tf.data.Datasets</a>, I see  that there is a frequent mention of "nested structures". What exactly is meant by that? Can any Python data type be considered a nested structure (e.g., <code>(1,3, (7,6, (0), 5))</code> or <code>dict(k=dict(3), 7, None</code>) or does this specifically refer to TensorFlow data types?</p>