An Approx class for unit testing float values similar to Catch2 (https://github.com/catchorg/Catch2/blob/master/docs/assertions.md#floating-point-comparisons)

Approx.py

class Approx(object):
  def __init__(self,val):
    self._val = val
    self._epsilon = 0.01
  def epsilon(self,epsilon):
    self._epsilon = epsilon
    return self
  def __eq__(self,other):
    return abs(other - self._val) <= self._epsilon*abs(other + self._val)/2