'Return the types which are expected to be conserved.'

def prepare_types_for_conservation_test(self):

    class MyFloat(float, ):
        def __truediv__(self, other):
            return type(self)(super().__truediv__(other))
        def __rtruediv__(self, other):
            return type(self)(super().__rtruediv__(other))
        def __sub__(self, other):
            return type(self)(super().__sub__(other))
        def __rsub__(self, other):
            return type(self)(super().__rsub__(other))
        def __pow__(self, other):
            return type(self)(super().__pow__(other))
        def __add__(self, other):
            return type(self)(super().__add__(other))
        __radd__ = __add__
    return (float, Decimal, Fraction, MyFloat)
