Unable to access nested list property

[arajkumar]

Code

        field = fields.Raw(attribute='bar.0')
        assert field.output('foo', {'bar': [42]}) == 42

Repro Steps (if applicable)

1. Try with above snippet

Expected Behavior

Properties which are nested under list should be accessible according to https://flask-restplus.readthedocs.io/en/stable/marshalling.html#renaming-attributes

Actual Behavior

A description of the unexpected, buggy behavior.

Error Messages/Stack Trace

No error/exception thrown, but it outputs None

Environment

• Python 3.6.9
• Flask 1.0.0
• Flask-RESTPlus 0.13.0
• Other installed Flask extensions - None