DOC: Make _field_accessor manage the docstring format
- [x] closes #24068 
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @charlesdong1991! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/arrays/datetimes.py`](https://github.com/charlesdong1991/pandas/blob/62d1599ac45d4da5a01858075d8e2f21958a229a/pandas/core/arrays/datetimes.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/timedeltas.py`](https://github.com/charlesdong1991/pandas/blob/62d1599ac45d4da5a01858075d8e2f21958a229a/pandas/core/arrays/timedeltas.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=h1) Report
> Merging [#24072](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/a7bb9720e969e1bb09165a2e3828b8ef70914196?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `87.5%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24072/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24072      +/-   ##
==========================================
+ Coverage   42.38%   42.39%   +<.01%     
==========================================
  Files         161      161              
  Lines       51699    51709      +10     
==========================================
+ Hits        21913    21920       +7     
- Misses      29786    29789       +3
```

| Flag | Coverage Δ | |
|---|---|---|
| #single | `42.39% <87.5%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24072/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `64.07% <100%> (+0.28%)` | :arrow_up: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24072/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `39.06% <75%> (+0.09%)` | :arrow_up: |
| [pandas/core/arrays/integer.py](https://codecov.io/gh/pandas-dev/pandas/pull/24072/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2ludGVnZXIucHk=) | `38.06% <0%> (+0.08%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24072?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/24072?src=pr&el=footer). Last update [a7bb972...62d1599](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=h1) Report
> Merging [#24072](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/a7bb9720e969e1bb09165a2e3828b8ef70914196?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `87.5%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24072/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24072      +/-   ##
==========================================
+ Coverage   42.38%   42.39%   +<.01%     
==========================================
  Files         161      161              
  Lines       51699    51709      +10     
==========================================
+ Hits        21913    21920       +7     
- Misses      29786    29789       +3
```

| Flag | Coverage Δ | |
|---|---|---|
| #single | `42.39% <87.5%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24072/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `64.07% <100%> (+0.28%)` | :arrow_up: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24072/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `39.06% <75%> (+0.09%)` | :arrow_up: |
| [pandas/core/arrays/integer.py](https://codecov.io/gh/pandas-dev/pandas/pull/24072/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2ludGVnZXIucHk=) | `38.06% <0%> (+0.08%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24072?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/24072?src=pr&el=footer). Last update [a7bb972...62d1599](https://codecov.io/gh/pandas-dev/pandas/pull/24072?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
