How the __name__ of a Python module be defined with different import method?

I'm struggling to understand how __name__ of a module be defined, especially in different import methods. Suppose a directory tree:

├ main.py
└ test/
  ├── __init__.py
  ├── a
  │   ├── a1.py
  │   ├── base.py    <- a1.py and b1.py will import it
  │   └── __init__.py
  └── b
      ├── b1.py
      └── __init__.py

And here is base.py:

# test/a/base.py
print("Base.py be imported, __name__ =", __name__)

a1.py imports base.py through relative import

# test/a/a1.py
print("[a1.py] import base: start")
from . import base
print("[a1.py] import base: end")

then a/__init__.py imports a1.py and base.py

# test/a/__init__.py
from . import base
from .a1 import *

For package b, the module b1.py import base through absolute import

# test/b/b1.py
print("[b1.py] import base: start")
from test.a import base
print("[b1.py] import base: end")

and b/__init__.py import b.py

# test/b/__init__.py
from test.b.b1 import *

Finally, the test/__init__.py will import both package a and b in different methods

# method1
print(" ----- import a -----")
from .a import *
print(" ----- import b -----")
from .b import *

# method2
import sys
import os
sys.path.append(os.path.dirname(os.path.abspath(__file__)) + "/./")
print(" ----- import a -----")
from a import *
print(" ----- import b -----")
from b import *

If I import test in main.py, the output looks like it in method1

----- import a -----
Base.py be imported!, __name__ =  test.a.base
[a1.py] import base: start
[a1.py] import base: end
----- import b -----
[b1.py] import base: start
[b1.py] import base: end

The __name__ of base is test.a.base. If I try it again in method2, the output looks like

----- import a -----
Base.py be imported!, __name__ =  a.base
[a1.py] import base: start
[a1.py] import base: end
----- import b -----
[b1.py] import base start
Base.py be imported!, __name__ =  test.a.base
[a1.py] import base: start
[a1.py] import base: end
[b1.py] import base: end

which is quite different to the method1.

How a module's __name__ be defined? Does different import method, like absolute/relative import or different import seaching path, change the module's __name__? I have seen this post but it still confuse me, and I want to know more about it under the hood. Thanks a lot!