" class="nav-link">Example 6: fir</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#example-7-iir" class="nav-link">Example 7: iir</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#example-8-comb-filter" class="nav-link">Example 8: comb filter</a>
              <ul class="nav flex-column">
              </ul>
            </l