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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 create(cls, selection, config, **kwargs):
 """Create an ROIModel instance."""


        if selection['target'] is not None:
            return cls.create_from_source(selection['target'],
                                          config, **kwargs)
        else:
            target_skydir = wcs_utils.get_target_skydir(selection)
            return cls.create_from_position(target_skydir, config, **kwargs)