> <span class="n">_this_roll</span><span class="p">)</span>
</span><span id="Sublosses.window_diff-45"><a href="#Sublosses.window_diff-45"><span class="linenos">45</span></a>        <span class="n">_n_shifts</span> <span class="o">=</span> <span class="n">tf</span><span class="o">.</span><span class="n">math</span><span class="o">.</span><span class="n">subtract</span><span class="p">(</span><span class="n">_n_shifts</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
</span><sp