r"""Sums up the flux from the pathways given

        Parameters
        -----------
        paths : list of int-arrays
        list of pathways

        pathfluxes : double-array
            array with path fluxes

        n : int
            number of states. If not set, will be automatically determined.

        Returns
        -------
        flux : (n,n) ndarray of float
            the flux containing the summed path fluxes

def _pathways_to_flux(self, paths, pathfluxes, n=None):
        r"""Sums up the flux from the pathways given

        Parameters
        -----------
        paths : list of int-arrays
        list of pathways

        pathfluxes : double-array
            array with path fluxes

        n : int
            number of states. If not set, will be automatically determined.

        Returns
        -------
        flux : (n,n) ndarray of float
            the flux containing the summed path fluxes

        """
        if (n is None):
            n = 0
            for p in paths:
                n = max(n, np.max(p))
            n += 1

        # initialize flux
        F = np.zeros((n, n))
        for i in range(len(paths)):
            p = paths[i]
            for t in range(len(p) - 1):
                F[p[t], p[t + 1]] += pathfluxes[i]
        return F