code: def update(self):
          
          con = self.subpars.pars.control
          self(con.eqb*con.tind)
docs: Update |KB| based on |EQB| and |TInd|.
  
          >>> from hydpy.models.lland import *
          >>> parameterstep('1d')
          >>> eqb(10.0)
          >>> tind.value = 10.0
          >>> derived.kb.update()
          >>> derived.kb
          kb(100.0)