Fix duplicated imports

[c-bata]

What this PR does / why we need it:

• Add __init__.py to avoid using namespace package.
  • See https://dev.to/methane/don-t-omit-init-py-3hga.
• Fix duplicated import problems by __all__ attribute.
  • To clarify this problem, I attached a screenshot of PyCharm.
  • 
  • logging is imported at L3 and used at L8. But Jetbrains IDE highlights import logging as gray. This means it is an unused line. The reason why it is highlighted as gray is using star imports ( from pkg.suggestion.v1alpha3.internal.search_space import * and from pkg.suggestion.v1alpha3.internal.trial import * ). To avoid this problem, I define __all__ attribute. See https://docs.python.org/3/tutorial/modules.html#importing-from-a-package

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
None

Special notes for your reviewer:

None

Release note:

NONE

[kubeflow-bot]

This change is 

[c-bata]

All star-imports are removed.

(venv) $ git co master
Switched to branch 'master'
Your branch is up to date with 'origin/master'.
(venv) $ git grep "import \*" | grep "\.py"
pkg/suggestion/v1alpha3/chocolate/base_chocolate_service.py:from pkg.suggestion.v1alpha3.internal.search_space import *
pkg/suggestion/v1alpha3/chocolate/base_chocolate_service.py:from pkg.suggestion.v1alpha3.internal.trial import *
pkg/suggestion/v1alpha3/hyperopt/base_hyperopt_service.py:from pkg.suggestion.v1alpha3.internal.search_space import *
pkg/suggestion/v1alpha3/hyperopt/base_hyperopt_service.py:from pkg.suggestion.v1alpha3.internal.trial import *
pkg/suggestion/v1alpha3/skopt/base_skopt_service.py:from pkg.suggestion.v1alpha3.internal.search_space import *
pkg/suggestion/v1alpha3/skopt/base_skopt_service.py:from pkg.suggestion.v1alpha3.internal.trial import *
(venv) $ git co fix-duplicated-imports
Switched to branch 'fix-duplicated-imports'
(venv) $ git grep "import \*" | grep "\.py"
(venv) $ 

[andreyvelich]

Thanks @c-bata !
/lgtm
/cc @gaocegege

[johnugeorge]

Can we do this in a better way to look more clean? we might have more constants. May be wrap this?

[c-bata]

You mean that you want to import all constants, right?
Another solution is to define __all__ attribute like this revision. But as the discussion of #1133 (comment), it is known as an anti-pattern in Python.

[andreyvelich]

@c-bata What do you think about creating file: constant.py under /internal/ folder ?
And insert all constant there? I think it will be easier to have all constant in one file

[c-bata]

It sounds good 👍 @johnugeorge What do you think?

[johnugeorge]

Yes. SGTM

[johnugeorge]

/lgtm
/approve

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