DOC: read_csv usecols element order is ignored
- [x] closes #18673
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18729?src=pr&el=h1) Report
> Merging [#18729](https://codecov.io/gh/pandas-dev/pandas/pull/18729?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c28b6249471ffddfed51d62437a65ca97766fb7f?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18729/graphs/tree.svg?width=650&height=150&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18729?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18729      +/-   ##
==========================================
- Coverage   91.64%   91.62%   -0.02%     
==========================================
  Files         154      154              
  Lines       51428    51428              
==========================================
- Hits        47129    47120       -9     
- Misses       4299     4308       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.49% <ø> (ø)` | :arrow_up: |
| #single | `40.83% <ø> (-0.12%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18729?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/18729/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.55% <ø> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18729/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18729/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.68% <0%> (-0.11%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18729?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18729?src=pr&el=footer). Last update [c28b624...0b3c0de](https://codecov.io/gh/pandas-dev/pandas/pull/18729?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @ignamv  You're welcome.