how to do this. Here is the corresponding trivial test:
    <pre>import custom_string
assert custom_string.hello() == "Hello world."
assert custom_string.size("california") == 10</pre>

    If you look at the code you will find:

    <ul>
    <li>A custom <tt>to_python</tt> converter (easy):
        <tt>custom_string_to_python_str</tt>

    <li>A custom lvalue converter (needs more code):
        <tt>custom_string_from_python_str</tt>
    </ul>

    The custom converters are registered in the global Boost.P