this here: <a class="link" href="../generator_concepts/nonterminal.html" title="Nonterminal"><code class="computeroutput"><span class="identifier">Nonterminal</span></code></a>.
                    </p>
                  </td>
<td>
                    <p>
                      <code class="computeroutput"><span class="identifier">unused_type</span></code>.
                      When <code class="computeroutput"><span class="identifier">Signature</span></code>
                      defaults to <code class="c