ion">
                        <h4>Declaration</h4>
                        <div class="language">
                          <p class="aside-title">Swift</p>
                          <pre class="highlight swift"><code><span class="kd">@available</span><span class="p">(</span><span class="o">*</span><span class="p">,</span> <span class="n">deprecated</span><span class="p">,</span> <span class="nv">message</span><span class="p">:</span> <span class="s">"Use `MutableReduceFunction` instead of `ReduceFunction`.