an class="n">query_tokens</span><span class="p">),</span> <span class="nb">len</span><span class="p">(</span><span class="n">key_tokens</span><span class="p">)):</span>
            <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;Attention matrix size should be equal to &#39;</span>
                             <span class="sa">f</span><span class="s1">&#39;[query_len, key_len] = [</span><span class="si">{</span><span class