(cls, x)
An expression for F(x) which holds for |x| < 1.
An expression for F(x) which holds for |x| < 1.
An expression for F ( x ) which holds for |x| < 1 .
def _expr_small(cls, x):
        """ An expression for F(x) which holds for |x| < 1. """
        raise NotImplementedError
def _expr_small ( cls , x ) : raise NotImplementedError