Drill custome function query

[honey francis]

Dear Drill team

I am writing a custom function which receives input from a Parquet file.
The file contains data which is in a JSON format. The custom function
requires a JSON element as input.

For example, I want pass the following JSON element(one of the elements of
the input JSON) to the custom function.

{"Fruits: [{"name":"Apples", "quantity":115},
            {"name":"Oranges","quantity":199},
            {"name":"Peaches", "quantity":116}
           ]
 }

Which holder class should I use in the custom function to read the input?

I tried VarcharHolder, ValueHolder etc. However, it is throwing the
following error.

    Error: Missing function implementation: [myFunction(MAP-REQUIRED)]

Can you please guide in reading the specified input in the custom function.

Thanks and Regards
Honey Francis