code: def hlog_inv(y, b=500, r=_display_max, d=_l_mmax):
      
      aux = 1. * d / r * y
      s = sign(y)
      if s.shape:  # to catch case where input is a single number
          s[s == 0] = 1
      elif s == 0:
          s = 1
      return s * 10 ** (s * aux) + b * aux - s
docs: Inverse of base 10 hyperlog transform.