Find all the member types that need custom unpackers.

Find all top-level types with the tilt:starlark-gen=true tag.

Opens the output file.

Writes the package header.

Given a gengo Type, create a starlark function that reads that type.

Writes a function that registers all the starlark methods.

Given a member struct type, we need to 3 pieces: 1) A starlark type so that this struct can be passed around.

Given a member list struct type, we need to 2 pieces: 1) A starlark type so that this struct can be passed around.