code: def update(self):
          
          mod = self.subpars.pars.model
          con = mod.parameters.control
          flu = mod.sequences.fluxes
          flu.h = con.hm
          mod.calc_qg()
          self(flu.qg)
docs: Update value based on the actual |calc_qg_v1| method.
  
          Required derived parameter:
              |H|
  
          Note that the value of parameter |lstream_derived.QM| is directly
          related to the value of parameter |HM| and indirectly related to
          all parameters values relevant for method |calc_qg_v1|. Hence the
          complete paramter (and sequence) requirements might differ for
          various application models.
  
          For examples, see the documentation on method ToDo.