Provide typing (type annotations) for generated python rule files

[lktslionel]

Context

WHEN

I use rdk to create a rule rule. It generates a few python files for the rule

I WANT TO

The generated code to have types annotations

SO THAT

I could benefits from static type checker like mypy or other linter to guide the development of my rules.

Proposed solutions

Solution 1: Add mypy stub files in the template for every suppport python runtime version

The mypy stub file will provide all type annotations for the provided helpers and boilerplate code.

rdk/
└── template/
    └── runtime/
        └── pythonX/
            ├── rule_code.py
            ├── rule_test.py
            └── rule_code.pyi # <- Mypy Stub file 

Solution 2: Add type annotation to the provided template

Here is an example using libraries:

• Boto3 Stubs
• AWS Powertools - Typing

# ...
from typing import Union, cast, Dict
from mypy_boto3_config.type_defs import ComplianceTypeType, EvaluationTypeDef
from aws_lambda_powertools.utilities.data_classes import AWSConfigRuleEvent

# ....
def evaluate_compliance(
    event: AWSConfigRuleEvent,
    configuration_item: Dict[str, Any],
    valid_rule_parameters: Dict[str, Any],
) -> Union[
    None,
    ComplianceTypeType,
    EvaluationTypeDef,
    List[EvaluationTypeDef],
]:
    ...

# This generates an evaluation for config
def build_evaluation(
    resource_id: str,
    compliance_type: ComplianceTypeType,
    event: AWSConfigRuleEvent,
    resource_type: str=DEFAULT_RESOURCE_TYPE,
    annotation: str=None,
) -> EvaluationTypeDef:
    ...
    return cast(EvaluationTypeDef, eval_cc)

I coud help implement this but I need to comment to make sure I'm on the right path.
Thanks in advance

Regards

[bmorrissirromb]

I think this type of work would be useful. Typing is a useful feature for ensuring code accuracy. If you submitted a PR, I would review it and try to push it through.