an> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">config</span><span class="o">.</span><span class="n">data_dir</span><span class="p">,</span> <span class="n">config</span><span class="o">.</span><span class="n">urls</span><span class="p">[</span><span class="s2">&quot;class_size&quot;</span><span class="p">]</span><span class="o">.</span><span class="n">filename_ptr</span><span class="p"