code: def disable_constant(parameterized):
      
      params = parameterized.params().values()
      constants = [p.constant for p in params]
      for p in params:
          p.constant = False
      try:
          yield
      except:
          raise
      finally:
          for (p, const) in zip(params, constants):
              p.constant = const
docs: Temporarily set parameters on Parameterized object to
      constant=False.