&#160;        <span class="keywordflow">return</span> std::nullopt;</div>
<div class="line"><a name="l00095"></a><span class="lineno">   95</span>&#160;    }</div>
<div class="line"><a name="l00096"></a><span class="lineno">   96</span>&#160; </div>
<div class="line"><a name="l00097"></a><span class="lineno">   97</span>&#160;    <span class="keyword">template</span> &lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a name="l00098"></a><span class="lineno">   98</span>&#160;    <span 