class="lineno">   83</span>&#160;        <span class="keyword">using</span> const_reference = <span class="keyword">typename</span> D::const_reference; <span class="comment">// == PixelConcept (if you remove const and reference)</span></div><div class="line"><a name="l00084"></a><span class="lineno">   84</span>&#160;</div><div class="line"><a name="l00085"></a><span class="lineno">   85</span>&#160;        <span class="keywordtype">bool</span> <span class="keyword">const</span> is_mutable = D::is_mutable;<