code: func (BitCurve *BitCurve) affineFromJacobian(x, y, z *big.Int) (xOut, yOut *big.Int) {
  	zinv := new(big.Int).ModInverse(z, BitCurve.P)
  	zinvsq := new(big.Int).Mul(zinv, zinv)
  
  	xOut = new(big.Int).Mul(x, zinvsq)
  	xOut.Mod(xOut, BitCurve.P)
  	zinvsq.Mul(zinvsq, zinv)
  	yOut = new(big.Int).Mul(y, zinvsq)
  	yOut.Mod(yOut, BitCurve.P)
  	return
  }
docs: //TODO: double check if the function is okay
  // affineFromJacobian reverses the Jacobian transform. See the comment at the
  // top of the file.