code: def calc_smoothpar_logistic2(metapar):
      
      if metapar <= 0.:
          return 0.
      return optimize.newton(_error_smoothpar_logistic2,
                             .3 * metapar**.84,
                             _smooth_logistic2_derivative,
                             args=(metapar,))
docs: Return the smoothing parameter corresponding to the given meta
      parameter when using |smooth_logistic2|.
  
      Calculate the smoothing parameter value corresponding the meta parameter
      value 2.5:
  
      >>> from hydpy.auxs.smoothtools import calc_smoothpar_logistic2
      >>> smoothpar = calc_smoothpar_logistic2(2.5)
  
      Using this smoothing parameter value, the output of function
      |smooth_logistic2| differs by
      1 % from the related `true` discontinuous step function for the
      input values -2.5 and 2.5 (which are located at a distance of 2.5
      from the position of the discontinuity):
  
      >>> from hydpy.cythons import smoothutils
      >>> from hydpy import round_
      >>> round_(smoothutils.smooth_logistic2(-2.5, smoothpar))
      0.01
      >>> round_(smoothutils.smooth_logistic2(2.5, smoothpar))
      2.51
  
      For zero or negative meta parameter values, a zero smoothing parameter
      value is returned:
  
      >>> round_(calc_smoothpar_logistic2(0.0))
      0.0
      >>> round_(calc_smoothpar_logistic2(-1.0))
      0.0