Can a single package define two modules inside a namespace package?

[tibbe]

Directory structure:

src/
  ns/
    pkg_a/
      __init__.py
      foo.py
    pkg_b/
      __init__.py
      bar.py

pyproject.toml:

[tool.poetry]
name = "pkg_a"
packages = [{include = "ns", from = "src"}]

This seems to work (i.e. I can poetry install this) but I see problems in other tools. For example, mypy reports

poetry run mypy -p ns.pkg_b                                              
Can't find package 'ns.pkg_b'

Now I don't expect this group to debug mypy issues but I'm just trying to understand if my package is a valid one. Can you have a package export two modules (pkg_a and pkg_b) under one namespace package (ns)?