Function pyo3::impl_::extract_argument::extract_optional_argument

#[doc(hidden)] pub fn extract_optional_argument<'a, 'py, T>(
    obj: Option<&'a Bound<'py, PyAny>>,
    holder: &'a mut T::Holder,
    arg_name: &str,
    default: fn() -> Option<T>
) -> PyResult<Option<T>>
where
    T: PyFunctionArgument<'a, 'py>,

Alternative to extract_argument used for Option<T> arguments. This is necessary because Option<&T> does not implement PyFunctionArgument for T: PyClass.