TensorFlow's target pruning can't find nodes
<p>I wrote a Python script using the TensorFlow API, including a <code>SummaryWriter</code> that dumps the graph definition so I can look at it in TensorBoard.</p>

<p>When running the script, a <code>NotFoundError</code> is thrown saying <code>PruneForTargets: Some target nodes not found: Reading/data_queue_EnqueueMany_1</code>. As its name implies, the node in question was created by an <code>enqueue_many</code> call on a <code>FIFOQueue</code> (which is then started in a <code>QueueRunner</code>); it does in fact exist, and can be seen clearly in TensorBoard.</p>

<p>What could cause TensorFlow to not find some nodes?</p>