code: def calc_inuz_v1(self):
      
      con = self.parameters.control.fastaccess
      der = self.parameters.derived.fastaccess
      flu = self.sequences.fluxes.fastaccess
      flu.inuz = 0.
      for k in range(con.nmbzones):
          if con.zonetype[k] != ILAKE:
              flu.inuz += der.rellandzonearea[k]*(flu.r[k]-flu.cf[k])
docs: Accumulate the total inflow into the upper zone layer.
  
      Required control parameters:
        |NmbZones|
        |ZoneType|
  
      Required derived parameters:
        |RelLandZoneArea|
  
      Required fluxes sequences:
        |R|
        |CF|
  
      Calculated flux sequence:
        |InUZ|
  
      Basic equation:
        :math:`InUZ = R - CF`
  
      Examples:
  
          Initialize three zones of different relative `land sizes`
          (area related to the total size of the subbasin except lake areas):
  
          >>> from hydpy.models.hland import *
          >>> parameterstep('1d')
          >>> nmbzones(3)
          >>> zonetype(FIELD, ILAKE, GLACIER)
          >>> derived.rellandzonearea = 2.0/3.0, 0.0, 1.0/3.0
          >>> fluxes.r = 6.0, 0.0, 2.0
          >>> fluxes.cf = 2.0, 0.0, 1.0
          >>> model.calc_inuz_v1()
          >>> fluxes.inuz
          inuz(3.0)
  
          Internal lakes do not contribute to the upper zone layer.  Hence
          for a subbasin consisting only of interal lakes a zero input
          value would be calculated:
  
          >>> zonetype(ILAKE, ILAKE, ILAKE)
          >>> model.calc_inuz_v1()
          >>> fluxes.inuz
          inuz(0.0)