 class="n">from_file</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="nb">format</span><span class="p">)</span>

    <span class="c1"># determine index of target sequence if necessary</span>
    <span class="c1"># (default: first sequence in alignment)</span>
    <span class="k">if</span> <span class="n">target_seq</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
        <span class="n">target_seq_index</span> <span class="o">=