Custom Functions in Query Transform

Hello DS Legends,

I have a question related to DS Custom Functions. I'm able to say "New Function Call" in Query transform output schema and call my function. But the custom function is outputting the field like below:

Is the "$" infront of the field name correct or Am I doing anything wrong?

Also, instead of doing like this, I would like to map the custom function to the output field. Is it possible in DS to do it that way?

I'm not sure if I'm clear. Please let me know if you have any questions.

Thanks

Pradeep