 return when it gets
          to the end of that block, or when it runs out of data. The <code class="computeroutput"><span class="identifier">Flush</span><span class="special">::</span><span class="identifier">block</span></code> option assists in appending to
          or combining deflate streams. Also to assist in this, on return <code class="computeroutput"><span class="identifier">write</span></code> will set <code class="computeroutput"><span class="identifier">zs</span><span class="special">.</span