support multiple return values using slice?

It should be possible in theory to support multiple return values from Go functions, constructing a []handle slice or something like that. The main problem would be supporting any kind of mix of basic value types (int, float etc) and objects requiring handles -- we don't have handles for values.. And, not sure about how pybindgen works with these -- it is targeted toward C / C++ which doesn't support multiple return types, so presumably it just ends up being a single opaque slice object return value, and it is up to the python user to decode the values properly.

Probably it would make the most sense to only support homogenous basic return values -- multiple int's floats etc. This is likely to be a very small subset of functions -- so far I have just written a few *Py methods that do this manually.

Note that the common case of an additional error return value is handled using a Python exception, instead of returning the error, so this would continue in any case.

首先检查现有手写的、返回多个值的 *Py 方法，以及 Go 函数如何通过 pybindgen 暴露。定义受支持的同质基本值情况，以及如何验证普通值、handles 和现有的基于异常的错误返回约定是否完成。

由索引模型根据 Issue 内容生成。