(docs update) Focusing on FromPy rather than IntoPy

[gilescope]

(as you get IntoPy for free)

Also try and point out that intoPy doesn't mean it's necessarily going to convert
something into a python object.

[gilescope]

(If I've got anything wrong please wade in!) Is there any way we can make things clearer? I just want to make sure the next person doesn't think IntoPy will definitely return a py object.

[davidhewitt]

This documentation looks good to me, thanks. I do agree that the naming of FromPy and IntoPy is potentially very confusing. I haven't at this point thought too hard about what a better design would be.

(E.g. I sort of wonder whether FromPy shouldn't exist, though I see why it does for symmetry with the types from std.)

[kngwyu]

Thank you!

[kngwyu]

I sort of wonder whether FromPy shouldn't exist, though I see why it does for symmetry with the types from std

We have various conversion traits.

1. Convert Rust object to Python object (Rust<->Python object). FromPyObject, FromPyPointer, FromPy
2. PyObject -> &'py PyAny conversion. AsPyRef
3. Downcast(any to dict, list or so). PyTryFrom

I don't think FromPy is an ideal name, but I think PyTryFrom is the most confusing name and should fix it as priority.