rectionalGraph.html">BidirectionalGraph</a> and supports <tt>in_edges</tt>, then so
does <tt>subgraph</tt>. Here we list all the functions that
<tt>subgraph</tt> could possibly support given a <tt>Graph</tt>
type that is a model of <a href="VertexListGraph.html">VertexListGraph</a>, <a href="EdgeListGraph.html">EdgeListGraph</a> and
<a href="BidirectionalGraph.html">BidirectionalGraph</a>. If the <tt>Graph</tt> type that you use
with <tt>subgraph</tt> does not model these concepts and supports
fewer functio