an class="n">spectrum_type</span><span class="p">)</span> <span class="k">function </span><span class="n">spectrum_mult_spectrum</span><span class="p">(</span><span class="n">self</span><span class="p">,</span><span class="n">s2</span><span class="p">)&amp;</span>
  <span class="k">result</span><span class="p">(</span><span class="n">spec</span><span class="p">)</span>
  <span class="c">!! Returns a product of two spectrum instances.</span>
  <span class="k">class</span><span class="p">(</span><span class="