code: def update(self):
          
          con = self.subpars.pars.control
          self(con.eqd2*con.tind)
docs: Update |KD2| based on |EQD2| and |TInd|.
  
          >>> from hydpy.models.lland import *
          >>> parameterstep('1d')
          >>> eqd2(0.1)
          >>> tind.value = 10.0
          >>> derived.kd2.update()
          >>> derived.kd2
          kd2(1.0)