test.py

class OneDTransform:
  def eval(self, r):
    raise NotImplementedError
  
  def inv(self, t):
     raise NotImplementedError
  
  def deriv1(self, r):
     raise NotImplementedError

class Inv(OneDTransform):
  def __init__(self, tf):
    self.tf = tf
  
  def eval(self, r):
    return self.tf.inv(r)

  def inv(self, t):
    return self.tf.eval(t)

  def deriv(self, r):
    return 1.0/self.tf.deriv(self.tf.inv(r))