docs: def netflux(self, a, b):
          r"""The netflux network for the reaction from
          A=[0,...,a] => B=[b,...,M].
  
          Parameters
          ----------
          a : int
              State index
          b : int
              State index
  
          Returns
          -------
          netflux : (M, M) ndarray
              Matrix of flux values between pairs of states.
  
          """
          flux = self.flux(a, b)
          netflux = flux - np.transpose(flux)
          ind = (netflux < 0.0)
          netflux[ind] = 0.0
          return netflux