span class="keyword">class</span><span class="special">...</span> Ts<span class="special">,</span> <span class="keyword">typename</span> U<span class="special">&gt;</span> 
          <span class="keyword">auto</span> <a class="link" href="../boost/histogram/axis/traits/update_idm45105994746512.html" title="Function template update"><span class="identifier">update</span></a><span class="special">(</span><a class="link" href="../boost/histogram/axis/variant.html" title="Class template variant">variant</a><spa