="keyword">virtual</span> <span class="keyword">const</span> std::optional&lt;bool&gt; isDirected() <span class="keyword">const</span>;</div>
<div class="line"><a name="l00051"></a><span class="lineno">   51</span>&#160;        <span class="keyword">virtual</span> <span class="keyword">const</span> std::optional&lt;bool&gt; isWeighted() <span class="keyword">const</span>;</div>
<div class="line"><a name="l00052"></a><span class="lineno">   52</span>&#160;        <span class="comment">//operator</span></div>