docs: def flux_matrix(T, pi, qminus, qplus, netflux=True):
      r"""Compute the TPT flux network for the reaction A-->B.
  
      Parameters
      ----------
      T : (M, M) ndarray
          transition matrix
      pi : (M,) ndarray
          Stationary distribution corresponding to T
      qminus : (M,) ndarray
          Backward comittor
      qplus : (M,) ndarray
          Forward committor
      netflux : boolean
          True: net flux matrix will be computed
          False: gross flux matrix will be computed
  
      Returns
      -------
      flux : (M, M) ndarray
          Matrix of flux values between pairs of states.
  
      Notes
      -----
      Computation of the flux network relies on transition path theory
      (TPT) [1]. Here we use discrete transition path theory [2] in
      the transition matrix formulation [3].
  
      See also
      --------
      committor.forward_committor, committor.backward_committor
  
      Notes
      -----
      Computation of the flux network relies on transition path theory
      (TPT). The central object used in transition path theory is the
      forward and backward comittor function.
  
      The TPT (gross) flux is defined as
  
      .. math:: f_{ij}=\left \{ \begin{array}{rl}
                            \pi_i q_i^{(-)} p_{ij} q_j^{(+)} & i \neq j \\
                            0                                & i=j\
                            \end{array} \right .
  
      The TPT net flux is then defined as
  
      .. math:: f_{ij}=\max\{f_{ij} - f_{ji}, 0\} \:\:\:\forall i,j.
  
      References
      ----------
      .. [1] W. E and E. Vanden-Eijnden.
          Towards a theory of transition paths.
          J. Stat. Phys. 123: 503-523 (2006)
      .. [2] P. Metzner, C. Schuette and E. Vanden-Eijnden.
          Transition Path Theory for Markov Jump Processes.
          Multiscale Model Simul 7: 1192-1219 (2009)
      .. [3] F. Noe, Ch. Schuette, E. Vanden-Eijnden, L. Reich and
          T. Weikl: Constructing the Full Ensemble of Folding Pathways
          from Short Off-Equilibrium Simulations.
          Proc. Natl. Acad. Sci. USA, 106, 19011-19016 (2009)
  
      """
      if issparse(T):
          return sparse.tpt.flux_matrix(T, pi, qminus, qplus, netflux=netflux)
      elif isdense(T):
          return dense.tpt.flux_matrix(T, pi, qminus, qplus, netflux=netflux)
      else:
          raise _type_not_supported