code: def reset_sum_fluxes(self):
          
          fluxes = self.sequences.fluxes
          for flux in fluxes.numerics:
              if flux.NDIM == 0:
                  setattr(fluxes.fastaccess, '_%s_sum' % flux.name, 0.)
              else:
                  getattr(fluxes.fastaccess, '_%s_sum' % flux.name)[:] = 0.
docs: Set the sum of the fluxes calculated so far to zero.
  
          >>> from hydpy.models.test_v1 import *
          >>> parameterstep()
          >>> fluxes.fastaccess._q_sum = 5.
          >>> model.reset_sum_fluxes()
          >>> fluxes.fastaccess._q_sum
          0.0