Add MICN modules and implement it as an imputation model

[WenjieDu]

What does this PR do?

1. fixing Add MICN #395;

Before submitting

• This PR is made to fix a typo or improve the docs (you can dismiss the other checks if this is the case).
• Was this discussed/approved via a GitHub issue? Please add a link to it if that's the case.
• I have commented my code, particularly in hard-to-understand areas.
• I have written necessary tests and already run them locally.

[coveralls]

Pull Request Test Coverage Report for Build 9052377252

Details

• 201 of 206 (97.57%) changed or added relevant lines in 9 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.3%) to 83.335%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pypots/imputation/micn/core.py	33	35	94.29%
pypots/imputation/micn/model.py	67	70	95.71%

Files with Coverage Reduction	New Missed Lines	%
pypots/cli/env.py	1	63.27%

Totals
Change from base Build 9051086823:	0.3%
Covered Lines:	9101
Relevant Lines:	10921

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💛 - Coveralls