'*limits* is the view limit of the data.  The only part of
its bounds that is used is ymax (for the radius maximum).
The theta range is always fixed to (0, 2pi).'

def __init__(self, scale_transform, limits):

    Affine2DBase.__init__(self)
    self._scale_transform = scale_transform
    self._limits = limits
    self.set_children(scale_transform, limits)
    self._mtx = None
