DOC: add dataframe construction in merge_asof example
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=h1) Report
> Merging [#16348](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4bdbcb638340a0529c2ddc7d3a85d0209004763f?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/16348/graphs/tree.svg?width=650&src=pr&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16348      +/-   ##
==========================================
- Coverage   90.38%   90.36%   -0.02%     
==========================================
  Files         161      161              
  Lines       50916    50916              
==========================================
- Hits        46021    46011      -10     
- Misses       4895     4905      +10
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.14% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.22% <ø> (-0.11%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `93.94% <ø> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.68% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.23% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16348?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/16348?src=pr&el=footer). Last update [4bdbcb6...7febec7](https://codecov.io/gh/pandas-dev/pandas/pull/16348?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/16348?src=pr&el=h1) Report
> Merging [#16348](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4bdbcb638340a0529c2ddc7d3a85d0209004763f?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/16348/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16348      +/-   ##
==========================================
- Coverage   90.38%   90.36%   -0.02%     
==========================================
  Files         161      161              
  Lines       50916    50916              
==========================================
- Hits        46021    46011      -10     
- Misses       4895     4905      +10
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.14% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.22% <ø> (-0.11%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `93.94% <ø> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.68% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.23% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16348?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/16348?src=pr&el=footer). Last update [4bdbcb6...7febec7](https://codecov.io/gh/pandas-dev/pandas/pull/16348?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
