docs: def totalflux(self, a, b):
          r"""The tiotal flux for the reaction
          A=[0,...,a] => B=[b,...,M].
  
          Parameters
          ----------
          a : int
              State index
          b : int
              State index
  
          Returns
          -------
          F : float
              The total flux between reactant and product
  
          """
          flux = self.flux(a, b)
          A = list(range(a + 1))
          notA = list(range(a + 1, flux.shape[0]))
          F = flux[A, :][:, notA].sum()
          return F