> <span class="identifier">pass_as_arg</span><span class="special">(</span><span class="identifier">expensive_to_copy</span><span class="special">*</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">PyObject</span><span class="special">*</span> <span class="identifier">f</span><span class="special">)</span>
<span class="special">{</span>
   <span class="comment">// call the Python function f, passing a Python object built around</span>
   <span class="comment">//