;</span> <span class="o">-</span><span class="mi">1</span> <span class="ow">or</span> \
       <span class="bp">self</span><span class="o">.</span><span class="n">dx_max</span> <span class="o">&gt;</span> <span class="mi">1</span> <span class="ow">or</span> <span class="bp">self</span><span class="o">.</span><span class="n">dy_max</span> <span class="o">&gt;</span> <span class="mi">1</span><span class="p">:</span>
      <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><