How to share stubs for type hinting transitively?

I am currently using a Python library (x) that does not come with type hints. I've opted to add stub files for the x methods that I use in my project like this:

MyProject_1/
  stubs/
    x/ 
      __init__.pyi  # Contains type hints for any attributes of `x`.

  package_1/
    package_1_main.py  # Imports `x`.
    __init__.py   
    py.typed  # Indicates package 1 type hints are specified inline.

  setup.py  # Specifies `x` as a dependency under `install_requires` and `py.typed` under `package_data`.

Then in the MyProject_1 directory, I run MYPYPATH=stubs mypy ..

If package_1_main.py imports x, then mypy successfully type hints the x imports based on stubs/x. All is good here.

Now I've made another project MyProject_2 that depends on MyProject_1 My_Project_2 successfully uses the inline type hints specified in package_1_main.py because of the py.typed under package_1.

The problem is that MyProject_2 does not pick up on stubs/x. Since x is a transitive dependency of MyProject_2 through MyProject_1, I have the ability to use x in MyProject_2. However, this is without the type hints specified under stubs/x.

There are 3 ways I can imagine being able to use these stubs (and thus access the type hints of x):

1. Add the stubs directory under MyProject_1 to the MYPYPATH when running mypy . in MyProject_2. Downside of this is it depends on how MyProject_1 was installed through pip, and stubs will have to be made as part of the distributed package data in setup.py.

2. Copy the stubs directory under MyProject_1 to MyProject_2, keeping them manually in sync. Downside of this is overhead in maintenance.

3. Make a third project called MyProject_Stubs, dedicated to keeping the stub files for any project depending on x, either transitively or directly. Downside of this is a dedicated project just for stubs.

Are there any other approaches I could consider? And for the slightly opinionated part: which one of these approaches seems to have the greatest net advantage?

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