It would be the base type for SqliteAggregateFunctionExpression, SqlServerAggregateFunctionExpression and [PgFunctionExpression](https://github.com/npgsql/efcore.pg/blob/main/src/EFCore.PG/Query/Expressions/Internal/PgFunctionExpression.cs)
It would be the base type for SqliteAggregateFunctionExpression, SqlServerAggregateFunctionExpression and PgFunctionExpression