code: def calc_qigz1_v1(self):
      
      con = self.parameters.control.fastaccess
      flu = self.sequences.fluxes.fastaccess
      sta = self.sequences.states.fastaccess
      sta.qigz1 = 0.
      for k in range(con.nhru):
          sta.qigz1 += con.fhru[k]*flu.qib1[k]
docs: Aggregate the amount of the first interflow component released
      by all HRUs.
  
      Required control parameters:
        |NHRU|
        |FHRU|
  
      Required flux sequence:
        |QIB1|
  
      Calculated state sequence:
        |QIGZ1|
  
      Basic equation:
         :math:`QIGZ1 = \\Sigma(FHRU \\cdot QIB1)`
  
      Example:
  
          >>> from hydpy.models.lland import *
          >>> parameterstep()
          >>> nhru(2)
          >>> fhru(0.75, 0.25)
          >>> fluxes.qib1 = 1.0, 5.0
          >>> model.calc_qigz1_v1()
          >>> states.qigz1
          qigz1(2.0)