code: def update(self):
          
          der = self.subpars
          self(numpy.clip(1. - der.c1 - der.c3, 0., 1.))
docs: Update |C2| based on :math:`c_2 = 1.-c_1-c_3`.
  
          Examples:
  
              The following examples show the calculated value of |C2| are
              clipped when to low or to high:
  
              >>> from hydpy.models.hstream import *
              >>> parameterstep('1d')
              >>> derived.c1 = 0.6
              >>> derived.c3 = 0.1
              >>> derived.c2.update()
              >>> derived.c2
              c2(0.3)
              >>> derived.c1 = 1.6
              >>> derived.c2.update()
              >>> derived.c2
              c2(0.0)
              >>> derived.c1 = -1.6
              >>> derived.c2.update()
              >>> derived.c2
              c2(1.0)