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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 buildDefaultRefWCS(self):
 """ Generate a default reference WCS for this image. """

        self.default_refWCS = None
        if self.use_wcs:
            wcslist = []
            for scichip in self.chip_catalogs:
                wcslist.append(self.chip_catalogs[scichip]['wcs'])
            self.default_refWCS = utils.output_wcs(wcslist)