/span>, desc <span class="op">=</span> <span class="st">"Taxes, supply"</span><span class="op">)</span> <span class="op">|&gt;</span> </span>
<span> <span class="fu"><a href="reference/add_variable.html">add_variable</a></span><span class="op">(</span><span class="st">"Y"</span>, desc <span class="op">=</span> <span class="st">"Income = GDP"</span><span class="op">)</span> <span class="op">|&gt;</span> </span>
<span> <span class="fu"><a href="reference/add_variable.html">add_variable</a></span><span class="