Nesting functions in expressions

Data Prepper
1

Hello,
I am trying to use a function in a function like this

- add_entries:
                  entries:
                    - metadata_key: "file_name"
                      value_expression: "/s3/key"

Then in routes :

route:
              -route1:  'contains(getMetadata("file_name"), "somefile")'

This gives error for invalid expression.
Is this even possible ?