def __init__(self, center=None, x_radius=1, y_radius=1, z_radius=0):
        '''
        :center:    - optional Point class initializer
        :x_radius:  - optional float
        :y_radius:  - optional float
        :z_radius:  - optional float

        Defaults to a unit ellipse centered on the origin.
        '''

        # XXX what does it mean to have non-zero radii in
        #     all three dimensions?

        self.center = center
        self.radius = x_radius, y_radius, z_radius
def __init__ ( self , center = None , x_radius = 1 , y_radius = 1 , z_radius = 0 ) : self . center = center self . radius = x_radius , y_radius , z_radius
:center:    - optional Point class initializer
        :x_radius:  - optional float
        :y_radius:  - optional float
        :z_radius:  - optional float

        Defaults to a unit ellipse centered on the origin.