r"""Returns the main pathway part of the net flux comprising
        at most the requested fraction of the full flux.

def major_flux(self, fraction=0.9):
        r"""Returns the main pathway part of the net flux comprising
        at most the requested fraction of the full flux.

        """
        (paths, pathfluxes) = self.pathways(fraction=fraction)
        return self._pathways_to_flux(paths, pathfluxes, n=self.nstates)