def make_multi(self) -> None:
        """Make a few source files we need for the tests."""
        self.make_file("multi.py", """\
            import a.a
            import b.b

            a.a.a(1)
            b.b.b(2)
            """)
        self.make_file("a/__init__.py")
        self.make_file("a/a.py", """\
            def a(x):
                if x == 1:
                    print("x is 1")
                else:
                    print("x is not 1")
            """)
        self.make_file("b/__init__.py")
        self.make_file("b/b.py", """\
            def b(x):
                msg = f"x is {x}"
                print(msg)
            """)
Make a few source files we need for the tests.
tests/test_annotate.py