lass="bp">self</span><span class="o">.</span><span class="n">threads</span> <span class="o">=</span> <span class="n">threads</span>

    <span class="c1"># Read input file</span>
    <span class="k">def</span> <span class="nf">_read_file</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="w">        </span><span class="sd">&quot;&quot;&quot;</span>
<span class="sd">        Read the input file and return the filtered transactions, primary items, and secondary item