Restyle get/list/import/api: subrepo support

[restyled-io]

A duplicate of #4247 with additional commits that automatically address
incorrect style, created by Restyled.

Since the original Pull Request was opened as a fork in a contributor's
repository, we are unable to create a Pull Request branching from it with only
the style fixes.

The following Restylers made fixes:

• black

To incorporate these changes, you can either:

1. Merge this Pull Request instead of the original, or

2. Ask your contributor to locally incorporate these commits and push them to
   the original Pull Request

   Expand for example instructions

   ```console
   git remote add upstream https://github.com/iterative/dvc.git
   git fetch upstream pull/<this PR number>/head
   git merge --ff-only FETCH_HEAD
   git push
   ```
   

NOTE: As work continues on the original Pull Request, this process will
re-run and update (force-push) this Pull Request with updated style fixes as
necessary. If the style is fixed manually at any point (i.e. this process finds
no fixes to make), this Pull Request will be closed automatically.

Sorry if this was unexpected. To disable it, see our documentation.

[codecov]

Codecov Report

Merging #4280 into master will decrease coverage by 0.28%.
The diff coverage is 90.06%.

@@            Coverage Diff             @@
##           master    #4280      +/-   ##
==========================================
- Coverage   91.72%   91.43%   -0.29%     
==========================================
  Files         173      175       +2     
  Lines       11747    11829      +82     
==========================================
+ Hits        10775    10816      +41     
- Misses        972     1013      +41     

Impacted Files	Coverage Δ
dvc/tree/_debug.py	0.00% <0.00%> (ø)
dvc/repo/tree.py	94.04% <91.56%> (+1.11%)	⬆️
dvc/api.py	96.15% <94.44%> (-1.53%)	⬇️
dvc/external_repo.py	89.55% <96.12%> (+2.00%)	⬆️
dvc/dependency/repo.py	100.00% <100.00%> (ø)
dvc/ignore.py	93.89% <100.00%> (-0.73%)	⬇️
dvc/repo/__init__.py	98.12% <100.00%> (+0.81%)	⬆️
dvc/repo/fetch.py	97.36% <100.00%> (+5.06%)	⬆️
dvc/repo/get.py	100.00% <100.00%> (ø)
dvc/repo/ls.py	97.91% <100.00%> (ø)
... and 18 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d346b8e...c84f4fd. Read the comment docs.