[pymvpa] SOM with custom distance metric

[Alan Johnson]

I'd like to use the PyMVPA self-organizing map module, but with a different distance metric for input vectors besides Euclidean.  Looking at the source code of som.py, can I subclass SimpleSOMMapper, just changing _get_bmu()?  On a more theoretical note, does the metric need to strictly be a metric, as opposed to a dissimilarity measure?

Thanks,
Alan