Parse signature with default value as python default value

[Xinihiko]

Hi, I have a problem in the generated .pyi results, where it wouldn't show the default value and making the Option<...>
Thus I have added the ability for creating below snippet from the

lib.rs

#[gen_stub_pyfunction]
#[pyfunction(signature=(x=0, y=0))]
fn add_two_number(x: i32, y: i32) -> i32 {...}

#[gen_stub_pyfunction]
#[pyfunction(signature=(numbers, precision=None))]
fn calculate_average(numbers: Vec<f64>, precision: Option<usize>) -> f64 {...}

pyi

def add_two_number(x:int = 0, y:int = 0) -> int:
    ...

def calculate_average(numbers:typing.Sequence[float], precision:typing.Optional[int] = None) -> float:
    ...

which previously was (in the python side we couldn't see the default value)

def add_two_number(x:int = ..., y:int = ...) -> int:
    ...

def calculate_average(numbers:typing.Sequence[float], precision:typing.Optional[int] = ...) -> float:
    ...

helper

(function) def add_two_number(
    x: int = 0,
    y: int = 0
) -> int

(function) def calculate_average(
    numbers: Sequence[float],
    precision: int | None = None
) -> float

I think some of this is caused by the changes made in the pyo3 which changes the Option<..> not to have default value of None
I would hope this could help the autocomplete in the python side.

If there is anything not fit your code structure or any changes need to be made, please let me know.
Thank you in advance

[konn]

Sorry for very late response. I think this is subsumed and addressed in #135 in more robust way. Thank you for your PR and very sorry for our late response 🙇