Nit about the decorator of PortArgs.init_new

[glen-amd]

Trivial issues:

1. From both the definition and the usage of PortArgs.init_new(), it may be better to be decorated with staticmethod rather than classmethod.
2. Even for a classmethod, the convention is typically using cls instead of self.

Motivation

Modifications

Checklist

• Format your code according to the Contributor Guide.
• Add unit tests as outlined in the Contributor Guide.
• Update documentation as needed, including docstrings or example tutorials.

[merrymercy]

Thanks @glen-amd. It is merged.