m unlock/lock
    wrapping of every time Boost.Python enters your code. You must
    furthermore take care to <i>not</i> unlock/lock when Boost.Python
    is invoking iterator changes via <tt>invoke.hpp</tt>.</p>
    <p>
    There is a patched <tt>invoke.hpp</tt> posted on the C++-SIG
    mailing list archives and you can find a real implementation of all
    the machinery necessary to fully implement this in the TnFOX
    project at <a href="http://sourceforge.net/projects/tnfox/"> this
    SourceForge pro