DOC: update the axes, shape, dim and size property docstring (Seoul)
This change includes the following property axes, shape, ndim, size

Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

- [X] PR title is "DOC: update the <your-function-or-method> docstring"
- [X] The validation script passes: `scripts/validate_docstrings.py <your-function-or-method>`
- [X] The PEP8 style check passes: `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] The html version looks good: `python doc/make.py --single <your-function-or-method>`
- [X] It has been proofread on language by another sprint participant

Please include the output of the validation script below between the "```" ticks:

```
# paste output of "scripts/validate_docstrings.py <your-function-or-method>" here
# between the "```" (remove this comment, but keep the "```")

$ scripts/validate_docstrings.py pandas.DataFrame.axes

################################################################################
###################### Docstring (pandas.DataFrame.axes)  ######################
################################################################################

Return a list representing the row axis labels and column axis labels
as the only members. They are returned in that order.

Examples
--------
>>> df = pd.DataFrame({'col1': [1, 2], 'col2': [3, 4]})
>>> df.axes
[RangeIndex(start=0, stop=2, step=1), Index(['coll', 'col2'],
dtype='object')]

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	No summary found (a short summary in a single line should be present at the beginning of the docstring)
	No returns section found
	See Also section not found
	Examples do not pass tests

################################################################################
################################### Doctests ###################################
################################################################################

**********************************************************************
Line 8, in pandas.DataFrame.axes
Failed example:
    df.axes
Expected:
    [RangeIndex(start=0, stop=2, step=1), Index(['coll', 'col2'],
    dtype='object')]
Got:
    [RangeIndex(start=0, stop=2, step=1), Index(['col1', 'col2'], dtype='object')]


$ scripts/validate_docstrings.py pandas.DataFrame.ndim

################################################################################
###################### Docstring (pandas.DataFrame.ndim)  ######################
################################################################################

Return an int representing the number of axes / array dimensions.

Examples
--------
>>> df = pd.DataFrame({'col1': [1, 2], 'col2': [3, 4]})
>>> df.ndim
2

>>> df = pd.DataFrame({'col1': [1, 2, 3], 'col2': [4, 5, 6],
...                    'col3': [7, 8, 9]})
>>> df.ndim
2

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	No extended summary found
	No returns section found
	See Also section not found


$ scripts/validate_docstrings.py pandas.DataFrame.size

################################################################################
###################### Docstring (pandas.DataFrame.size)  ######################
################################################################################

Return a numpy.int64 representing the number of elements
in this object.

Examples
--------
>>> df = pd.DataFrame({'col1': [1, 2], 'col2': [3, 4]})
>>> df.size
4

>>> df = pd.DataFrame({'col1': [1, 2, 3], 'col2': [4, 5, 6],
...                    'col3': [7, 8, 9]})
>>> df.size
9

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	No summary found (a short summary in a single line should be present at the beginning of the docstring)
	No returns section found
	See Also section not found


$ scripts/validate_docstrings.py pandas.DataFrame.shape

################################################################################
###################### Docstring (pandas.DataFrame.shape) ######################
################################################################################

Return a tuple representing the dimensionality of the DataFrame.

Examples
--------
>>> df = pd.DataFrame({'col1': [1, 2], 'col2': [3, 4]})
>>> df.shape
(2, 2)

>>> df = pd.DataFrame({'col0': [1, 2, 3], 'col2': [4, 5, 6],
...                    'col3': [7, 8, 9]})
>>> df.shape
(3, 3)

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	No extended summary found
	No returns section found
	See Also section not found
```

If the validation script still gives errors, but you think there is a good reason
to deviate in this case (and there are certainly such cases), please state this
explicitly.

Current change [1][2][3][4] occurred following error "No returns section found", "See Also section nod found". 
Because this function is property. so I did not make Return and Also section.
And then axes[1] property occurred "Examples do not pass tests". I made a newline in the result to avoid flake8 error. It raises the above error.

[1] pandas.DataFrame.axes
[2] pandas.DataFrame.ndim
[3] pandas.DataFrame.size
[4] pandas.DataFrame.shape
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20101?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@840d432`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/20101/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/20101?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #20101   +/-   ##
=========================================
  Coverage          ?   91.72%           
=========================================
  Files             ?      150           
  Lines             ?    49149           
  Branches          ?        0           
=========================================
  Hits              ?    45083           
  Misses            ?     4066           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.11% <ø> (?)` | |
| #single | `41.85% <ø> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/20101?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/20101/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.18% <ø> (ø)` | |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/20101/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.84% <ø> (ø)` | |

------

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 @yeongseon Thanks a lot! @jorisvandenbossche  No problem.