ALAD method implemented

[mbongaerts]

Implemented the ALAD method

paper: https://arxiv.org/pdf/1812.02288.pdf

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• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
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All Submissions Cores:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
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• [x] Have you created a <NewModel>.py in ~/pyod/models/?
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[mbongaerts]

@houssamzenati, I made an implementation of the ALAD method for pyOD. It would be great if you could review it. Thanks!

[coveralls]

Pull Request Test Coverage Report for Build 2730406361

• 276 of 329 (83.89%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 95.435%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyod/test/test_alad.py	79	80	98.75%
pyod/models/alad.py	197	249	79.12%
<!--	Total:	276	329

Totals
Change from base Build 2618158103:	-0.5%
Covered Lines:	7882
Relevant Lines:	8259

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💛 - Coveralls

[yzhao062]

sorry there will be some delay on my end to multiple ddl...will review very soon!! thanks

[mbongaerts]

sorry there will be some delay on my end to multiple ddl...will review very soon!! thanks

No problem! Thanks!