       <tt>C[-1]</tt> indexes the rightmost element in <tt>C</tt>).
        <strong><tt>convert_index</tt></strong> should handle the necessary
        conversion for the C++ container (e.g. convert <tt>-1</tt> to
        <tt>C.size()-1</tt>). <tt><strong>convert_index</strong></tt> should
        also be able to convert the type of the index (A dynamic Python type)
        to the actual type that the C++ container expects.
      </p>
      <p>
        When a container expands or contracts, held indexes to 