code: def filter_symlog(y, base=10.0):
      
      log_base = np.log(base)
      sign = np.sign(y)
      logs = np.log(np.abs(y) / log_base)
      return sign * logs
docs: Symmetrical logarithmic scale.
  
      Optional arguments:
  
      *base*:
          The base of the logarithm.