span class="identifier">assert</span><span class="special">(</span><span class="number">1</span> <span class="special">==</span> <span class="identifier">omap</span><span class="special">.</span><span class="identifier">erase</span><span class="special">(</span><span class="identifier">i</span><span class="special">));</span>
      <span class="identifier">assert</span><span class="special">(</span><span class="number">1</span> <span class="special">==</span> <span class="identifier">umap</span><span class=