code: def get_radial_circles(self):
          
          circles = ffi.new('double[6]')
          _check_status(cairo.cairo_pattern_get_radial_circles(
              self._pointer,  circles + 0, circles + 1, circles + 2,
              circles + 3, circles + 4, circles + 5))
          return tuple(circles)
docs: Return this radial gradient’s endpoint circles,
          each specified as a center coordinate and a radius.
  
          :returns: A ``(cx0, cy0, radius0, cx1, cy1, radius1)`` tuple of floats.