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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def to_pixel(self, wcs, mode='all'):
 """ Convert the aperture to a `CircularAperture` object defined in pixel coordinates. Parameters wcs : `~astropy.wcs.WCS` The world coordinate system (WCS) transformation to use. mode : {'all', 'wcs'}, optional Whether to do the transformation including distortions (``'all'``; default) or only including only the core WCS transformation (``'wcs'``). Returns ------- aperture : `CircularAperture` object A `CircularAperture` object. """


        pixel_params = self._to_pixel_params(wcs, mode=mode)
        return CircularAperture(**pixel_params)