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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 _get_prtflds(self):
 """Get print fields for GO header."""

        # User-specified print fields
        ntflds = self.gosubdag.prt_attr['flds']
        prt_flds = self.kws.get('prt_flds')
        if prt_flds:
            return prt_flds.intersection(ntflds)
        exclude = set()
        # Default print fields
        if self.gosubdag.relationships:
            exclude.add('level')
        return set(f for f in ntflds if f not in exclude)