code: def calc_qigz2_v1(self):
      
      con = self.parameters.control.fastaccess
      flu = self.sequences.fluxes.fastaccess
      sta = self.sequences.states.fastaccess
      sta.qigz2 = 0.
      for k in range(con.nhru):
          sta.qigz2 += con.fhru[k]*flu.qib2[k]
docs: Aggregate the amount of the second interflow component released
      by all HRUs.
  
      Required control parameters:
        |NHRU|
        |FHRU|
  
      Required flux sequence:
        |QIB2|
  
      Calculated state sequence:
        |QIGZ2|
  
      Basic equation:
         :math:`QIGZ2 = \\Sigma(FHRU \\cdot QIB2)`
  
      Example:
  
          >>> from hydpy.models.lland import *
          >>> parameterstep()
          >>> nhru(2)
          >>> fhru(0.75, 0.25)
          >>> fluxes.qib2 = 1.0, 5.0
          >>> model.calc_qigz2_v1()
          >>> states.qigz2
          qigz2(2.0)