Fix typehint and address the mypy errors of src/lerobot/configs

[tetsugo02]

Added type hint and ensure the lerobot/configs modules pass the mypy check

Fixes #1730

Changes

In this pr, I mainly fixed the mypy error, so I test my changes by using mypy and pre-commit
I changed pyproject.toml and .pre-commit-config as follows.

#pyproject.toml
# uncomment the follow block
[tool.mypy]
python_version = "3.10"
warn_return_any = true
warn_unused_configs = true
ignore_missing_imports = false

# .pre-commit-config.yaml
# uncomment the fellow block
  - repo: https://github.com/pre-commit/mirrors-mypy
    rev: v1.16.0
    hooks:
      - id: mypy
        args: [--python-version=3.10, --follow-imports=silent]
        files: ^src/lerobot/configs/
        additional_dependencies:
          ["numpy", "torch", "huggingface_hub", "draccus"]

How it was tested

pre-commit

In this pr, I mainly fixed the mypy error, you can test the changes by using:

pre-commit run mypy --all-files 

mypy

mypy --check-untyped-defs  src/lerobot/configs/ 

Added type: ignore

• src/lerobot/configs/train:
  • Used third-party library uses Any as return type
• src/lerobot/configs/train
  • The parent class TrainPipelineConfig defined the dataset' type as DatasetConfig. And this property is used in many places. It was difficult to change.
• src/lerobot/configs/policies
  • The parent class having a same name method makes here error, but the push_to_hub is also used in many places.

[Copilot]

Pull Request Overview

This PR fixes type hint issues and addresses mypy errors in the src/lerobot/configs module to ensure the codebase passes mypy static type checking.

• Adds proper type annotations to function return types and variables
• Fixes mypy errors related to assignment and type mismatches
• Improves error handling by raising exceptions instead of printing messages
• Adds null checks and proper handling for optional parameters

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/lerobot/configs/train.py	Adds type hints, improves validation logic with null checks, and fixes assignment issues
src/lerobot/configs/policies.py	Adds type annotations and converts print statement to proper exception raising
src/lerobot/configs/parser.py	Adds return type annotations and null safety checks for argument filtering
src/lerobot/configs/eval.py	Adds null safety checks for policy attribute access

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[tetsugo02]

Hello,
I am new to OSS, and this is my first attempt at contributing to this project.
I would appreciate any feedback. Thanks.

[AdilZouitine]

LGTM, I'm waiting the review of one more team member to approve and precommit hook pass!
Thanks for the contribution!