code: def calc_ag_v1(self):
      
      flu = self.sequences.fluxes.fastaccess
      flu.ag = flu.am+flu.av[0]+flu.av[1]+flu.avr[0]+flu.avr[1]
docs: Sum the through flown area of the total cross section.
  
      Required flux sequences:
        |AM|
        |AV|
        |AVR|
  
      Calculated flux sequence:
        |AG|
  
      Example:
  
          >>> from hydpy.models.lstream import *
          >>> parameterstep()
          >>> fluxes.am = 1.0
          >>> fluxes.av= 2.0, 3.0
          >>> fluxes.avr = 4.0, 5.0
          >>> model.calc_ag_v1()
          >>> fluxes.ag
          ag(15.0)