code: def jukesCantorD(p, L=100):
      
      assert 0 <= p < .75
  
      rD = 1 - 4. / 3 * p
      D = -.75 * log(rD)
      varD = p * (1 - p) / (rD ** 2 * L)
  
      return D, varD
docs: >>> jukesCantorD(.1)
      (0.10732563273050497, 0.001198224852071006)
      >>> jukesCantorD(.7)
      (2.0310376508266565, 0.47249999999999864)