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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_primary_key_columns(self):
 """ Returns the primary key columns. :rtype: list """

        if not self.has_primary_key():
            raise DBALException('Table "%s" has no primary key.' % self.get_name())

        return self.get_primary_key().get_columns()