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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_keys(self):
 """Returns the primary keys referenced in user supplied model"""

        res = []
        for column in self.column_definitions:
            if 'primary_key' in column.keys():
                tmp = column.get('primary_key', None)
                res.append(column['name']) if tmp else False
        return res