[autodoc] Parse PEP 257 style docstring

[vwxyzjn]

Copied from https://github.com/rr-/docstring_parser/issues/71#issue-1318744037

The approved PEP 257 mentions the so-called "attribute docstrings", which are string literals in the line after where an attribute is defined. These kind of docstrings are supported by a several packages, for example sphinx's autodoc extension.

An example looks like below:

from dataclasses import dataclass
from typing import Optional
from docstring_parser import parse_from_object

@dataclass
class RewardConfig:
    """
    RewardConfig collects all training arguments related to the [`RewardTrainer`] class.
    """

    max_length: Optional[int] = None
    """The maximum length of the sequences in the batch. This argument is required if you want to use the default data collator."""
    gradient_checkpointing: Optional[bool] = True
    """If True, use gradient checkpointing to save memory at the expense of slower backward pass."""

doc = parse_from_object(RewardConfig)

print(doc.short_description)
print()
for i in doc.params:
    print(f"{i.arg_name}, {i.type_name} (default - {i.default})\n   {i.description}")
    print()

RewardConfig collects all training arguments related to the [`RewardTrainer`] class.

max_length, Optional[int] (default - None)
   The maximum length of the sequences in the batch. This argument is required if you want to use the default data collator.

gradient_checkpointing, Optional[bool] (default - True)
   If True, use gradient checkpointing to save memory at the expense of slower backward pass.

This appears not supported in the autodoc feature of this repo. For example, in TRL our config is https://github.com/huggingface/trl/blob/d608fea0d107d4359f9c03a9d6dd434d292a9f50/trl/trainer/ppo_config.py, but its related docs does not show the documentation.