  </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#example-1-ramp" class="nav-link">Example 1: Ramp</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#semantics" class="nav-link">Semantics</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#example-2-a-phase-signal" class="nav-link">Example 2: a