[doc] chore: improve docstring consistency in device.py

[yurekami]

Summary

Part of the effort to improve docstring consistency across the verl codebase as described in #1345.

This PR focuses on verl/utils/device.py which had several functions with incomplete or missing docstrings.

Changes:

• Added proper Returns sections with type information to all functions
• Added missing docstrings to:
  • auto_set_ascend_device_name()
  • get_device_capability()
• Improved existing docstrings for clarity and consistency
• Fixed type annotation on get_torch_device() (removed invalid any type hint)
• Follows Google-style format which is the dominant style in the codebase

Style Note

Based on investigation of the codebase, Google-style docstrings are already the most commonly used format. This PR follows that convention rather than NumPy style, to maintain consistency with existing code.

Test plan

• Syntax check passes
• No functional changes - documentation only

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request improves docstring consistency in verl/utils/device.py by adding and updating docstrings to follow the Google-style format, and fixing an invalid type hint. The changes significantly improve code readability and documentation. I've provided a couple of suggestions to further improve type hint correctness, which will enhance type safety and maintainability.

[gemini-code-assist]

While removing the invalid any type hint is a good fix, it would be even better to provide a correct type hint for this function to improve type safety and code clarity. Since this function returns a module, you could use Any from the typing module or types.ModuleType from the types module.

For example:

from typing import Any

def get_torch_device() -> Any:
    # ...

This would make the function's return type explicit.

[gemini-code-assist]

The return type hint tuple[int, int] is incorrect. As the docstring correctly states, when CUDA is not available, this function returns (None, None). The type hint should be tuple[int | None, int | None] to reflect that the values can be None.

Suggested change

	def get_device_capability(device_id: int = 0) -> tuple[int, int]:
	def get_device_capability(device_id: int = 0) -> tuple[int | None, int | None]:

[wuxibin89]

@yurekami Please resolve conflict