c_trace : 
  <span>?desc_of_source:<span>( <span><a href="Source/index.html#type-t">Source.t</a> <span class="arrow">&#45;&gt;</span></span> string )</span> <span class="arrow">&#45;&gt;</span></span>
  <span>?source_should_nest:<span>( <span><a href="Source/index.html#type-t">Source.t</a> <span class="arrow">&#45;&gt;</span></span> bool )</span> <span class="arrow">&#45;&gt;</span></span>
  <span>?desc_of_sink:<span>( <span><a href="Sink/index.html#type-t">Sink.t</a> <span class="arrow">&#45;&gt;</span></s