ow">in</span> <span class="n">hydrogens</span><span class="p">:</span>
                        <span class="n">grp_hs</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">neighbor</span><span class="p">)</span>
            <span class="n">func_grp</span> <span class="o">=</span> <span class="n">func_grp</span><span class="o">.</span><span class="n">union</span><span class="p">(</span><span class="n">grp_hs</span><span class="p">)</span>

            <span class="n"