[PyYAML] Use Incomplete instead of Any

[donbarbos]

In some places, Any was intended to represent a Python object corresponding to a YAML value.
I think we could be more precise than simply using Any here for example, by defining a TypeAlias for the possible types (list, dict, etc.) and adding a comment explaining the choice.

[srittau]

In some places, Any was intended to represent a Python object corresponding to a YAML value.
I think we could be more precise than simply using Any here for example, by defining a TypeAlias for the possible types (list, dict, etc.) and adding a comment explaining the choice.

In general a type alias would also double as documentation and would make the comment for Any superfluous. But we probably need to distinguish between output types (= Any) and input types (= X | Y) for the usual union in output types problem.