type</span><span class="p">)</span> <span class="k">function </span><span class="n">integrate_spectrum</span><span class="p">(</span><span class="n">func</span><span class="p">,</span><span class="n">initial</span><span class="p">,</span><span class="n">tendency</span><span class="p">,</span><span class="n">dt</span><span class="p">)</span>
  <span class="c">!! Integrates spectrum forward in time using a time integration method</span>
  <span class="c">!! provided as the argument `func`.</span>
  <span clas