Deprecate the support of python 3.6

[fangyixiao18]

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Motivation

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Modification

Please briefly describe what modification is made in this PR.

BC-breaking (Optional)

Does the modification introduce changes that break the backward compatibility of the downstream repositories? If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

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Checklist

Before PR:

• [ ] Pre-commit or other linting tools are used to fix the potential lint issues.
• [ ] Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• [ ] The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• [ ] The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• [ ] If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects, like MMDet or MMSeg.
• [ ] CLA has been signed and all committers have signed the CLA in this PR.

[codecov[bot]]

Codecov Report

Base: 81.84% // Head: 80.49% // Decreases project coverage by -1.35% :warning:

Coverage data is based on head (916eff5) compared to base (a1f1dad). Patch coverage: 74.04% of modified lines in pull request are covered.

:exclamation: Current head 916eff5 differs from pull request most recent head 9731b93. Consider uploading reports for the commit 9731b93 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev-1.x #657 +/- ## =========================================== - Coverage 81.84% 80.49% -1.36% =========================================== Files 120 141 +21 Lines 4176 5056 +880 Branches 586 671 +85 =========================================== + Hits 3418 4070 +652 - Misses 645 851 +206 - Partials 113 135 +22 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `80.49% <74.04%> (-1.36%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab) | Coverage Δ | | |---|---|---| | [mmselfsup/datasets/transforms/\_\_init\_\_.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL2RhdGFzZXRzL3RyYW5zZm9ybXMvX19pbml0X18ucHk=) | `100.00% <ø> (ø)` | | | [mmselfsup/datasets/transforms/wrappers.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL2RhdGFzZXRzL3RyYW5zZm9ybXMvd3JhcHBlcnMucHk=) | `100.00% <ø> (ø)` | | | [mmselfsup/engine/hooks/deepcluster\_hook.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL2VuZ2luZS9ob29rcy9kZWVwY2x1c3Rlcl9ob29rLnB5) | `38.88% <0.00%> (-0.55%)` | :arrow_down: | | [mmselfsup/engine/optimizers/lars.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL2VuZ2luZS9vcHRpbWl6ZXJzL2xhcnMucHk=) | `16.12% <ø> (ø)` | | | [mmselfsup/models/algorithms/odc.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL21vZGVscy9hbGdvcml0aG1zL29kYy5weQ==) | `31.70% <ø> (ø)` | | | [mmselfsup/models/backbones/mae\_vit.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL21vZGVscy9iYWNrYm9uZXMvbWFlX3ZpdC5weQ==) | `100.00% <ø> (ø)` | | | [mmselfsup/models/backbones/simmim\_swin.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL21vZGVscy9iYWNrYm9uZXMvc2ltbWltX3N3aW4ucHk=) | `86.95% <ø> (ø)` | | | [mmselfsup/models/heads/latent\_heads.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL21vZGVscy9oZWFkcy9sYXRlbnRfaGVhZHMucHk=) | `100.00% <ø> (ø)` | | | [mmselfsup/models/losses/swav\_loss.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL21vZGVscy9sb3NzZXMvc3dhdl9sb3NzLnB5) | `83.01% <ø> (ø)` | | | [mmselfsup/models/necks/densecl\_neck.py](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab#diff-bW1zZWxmc3VwL21vZGVscy9uZWNrcy9kZW5zZWNsX25lY2sucHk=) | `85.71% <ø> (ø)` | | | ... and [83 more](https://codecov.io/gh/open-mmlab/mmselfsup/pull/657?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-mmlab)

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