Returns the 'DBMS Version' string, or ''. If a connection to the
        database has not already been established, a connection will be made
        when `make_connection` is True.

def __get_dbms_version(self, make_connection=True):
        """
        Returns the 'DBMS Version' string, or ''. If a connection to the
        database has not already been established, a connection will be made
        when `make_connection` is True.
        """
        if not self.connection and make_connection:
            self.connect()
        with self.connection.cursor() as cursor:
            cursor.execute("SELECT SERVERPROPERTY('productversion')")
            return cursor.fetchone()[0]