Proportional probability method.

def _forwardImplementation(self, inbuf, outbuf):
        """ Proportional probability method.
        """
        assert self.module

        propensities = self.module.getActionValues(0)

        summedProps = sum(propensities)
        probabilities = propensities / summedProps

        action = eventGenerator(probabilities)
#        action = drawIndex(probabilities)

        outbuf[:] = scipy.array([action])