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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 primary_measures(self):
 """Iterate over the primary columns, columns which do not have a parent Also sets the property partition_stats to the stats collection for the partition and column. """

        from ambry.valuetype.core import ROLE

        for c in self.columns:

            if not c.parent and c.role == ROLE.MEASURE:
                    yield c