从Java API执行功能

Question

文档https://orientdb.com/docs/3.0.x/admin/Functions-Use.html

new_df <- data.frame(xev=recode(df$x, 'a'=.01, 'b'=.02, 'c'=.03), y=df$y)

但在Java文档https://orientdb.com/javadoc/develop/com/orientechnologies/orient/core/metadata/function/OFunction.html

中

OFunction sum = db.getMetadata().getFunctionLibrary().getFunction("sum");

Number result = sum.execute(3, 5);

现在如何正确调用函数？ 谢谢