code: def trim(self, lower=None, upper=None):
          
          whc = self.subseqs.seqs.model.parameters.control.whc
          sp = self.subseqs.sp
          if (upper is None) and (sp.values is not None):
              upper = whc*sp
          hland_sequences.State1DSequence.trim(self, lower, upper)
docs: Trim values in accordance with :math:`WC \\leq WHC \\cdot SP`.
  
          >>> from hydpy.models.hland import *
          >>> parameterstep('1d')
          >>> nmbzones(7)
          >>> whc(0.1)
          >>> states.sp = 0.0, 0.0, 0.0, 5.0, 5.0, 5.0, 5.0
          >>> states.wc(-1.0, 0.0, 1.0, -1.0, 0.0, 0.5, 1.0)
          >>> states.wc
          wc(0.0, 0.0, 0.0, 0.0, 0.0, 0.5, 0.5)