def union(self):
usegs = reduce(operator.or_, self.values())<EOL>usegs.name = '<STR_LIT>'.join(self.keys())<EOL>return usegs<EOL>
Return the union of all flags in this dict

        Returns
        -------
        union : `DataQualityFlag`
            a new `DataQualityFlag` who's active and known segments
            are the union of those of the values of this dict