def vertices(self):
        '''
        A dictionary of four points where the axes intersect the ellipse, dict.
        '''
        return {'a': self.a, 'a_neg': self.a_neg,
                'b': self.b, 'b_neg': self.b_neg}
def vertices ( self ) : return { 'a' : self . a , 'a_neg' : self . a_neg , 'b' : self . b , 'b_neg' : self . b_neg }
A dictionary of four points where the axes intersect the ellipse, dict.