></strong> converts a Python index into

        a C++ index that the container can handle. For instance, negative

        indexes in Python, by convention, start counting from the right(e.g.

        <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