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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 as_sql(self):
 """ represent heading as SQL field list """

        return ','.join('`%s`' % name if self.attributes[name].sql_expression is None
                        else '%s as `%s`' % (self.attributes[name].sql_expression, name)
                        for name in self.names)