title: NetworkX recursive child nodes
body: <p>Using the latest NetworkX (<a href="https://networkx.readthedocs.io/en/stable/" rel="nofollow noreferrer">version 1.11</a> at the time of writing), what is the most efficient way of retrieving all (recursive) child nodes for a given node?<br>
  The <code>successors()</code> function retrieves the immediate children and in previous versions there was <a href="https://groups.google.com/forum/#!topic/networkx-discuss/SukXT4ZHrRk" rel="nofollow noreferrer"><code>dfs_preorder_nodes solution</code></a>.</p>