classes – List all class in python package

I try to list all class in a package I made. I try to do that but I get errors:
List all classes in a package directory

Here is my architecture:

---list.py
---pkg
---pkg/base.py
---pkg/foo.py
---pkg/__init__.py

In base.py :

class _MyBase(object):
    pass

In foo.py:

from .base import _MyBase

class Foo(_MyBase):
     pass

In list.py:

import os
import sys
import pkgutil
import importlib
from pkg import base

all_my_base_classes = {}
pkg_dir = 'my_current_project_absolute_path'
for (module_loader, name, ispkg) in pkgutil.iter_modules((pkg_dir)):
    print (module_loader)
    print (ispkg)
    print (name)
    importlib.import_module('./' + name, __package__)


all_my_base_classes = {cls.__name__: cls for cls in base._MyBase.__subclasses__()}

I get that error:

TypeError: the 'package' argument is required to perform a relative import for './base'

As in the post, I want to list all class that depends on _MyBase in directory and subdirectory of my package.

What did I do wrong?