an>
  <span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span>
  <span class=keyword>typename</span> <span class=identifier>IndexSpecifierList</span><span class=special>=</span><span class=identifier>indexed_by</span><span class=special>&lt;</span><span class=identifier>ordered_unique</span><span class=special>&lt;</span><span class=identifier>identity</span><span class=special>&lt;</span><span class=identifier>Value</span><span class=special>&gt;</span> <span clas