code: def update(self):
          
          parensemble = self.analysis_evensen()
          obsensemble  = self.forecast(parensemble=parensemble)
          # todo: check for phi improvement
          if True:
              self.obsensemble = obsensemble
              self.parensemble = parensemble
  
          self.iter_num += 1
docs: update performs the analysis, then runs the forecast using the updated self.parensemble.
          This can be called repeatedly to iterate...