[SPARK-46635][PYTHON][DOCS] Refine docstring of from_csv/schema_of_csv/to_csv

[LuciferYang]

What changes were proposed in this pull request?

This pr refine docstring of from_csv/schema_of_csv/to_csv and add some new examples.

Why are the changes needed?

To improve PySpark documentation

Does this PR introduce any user-facing change?

No

How was this patch tested?

Pass Github Actions

Was this patch authored or co-authored using generative AI tooling?

No

[LuciferYang]

Error: Internal server error occurred while resolving "actions/cache@v3". Internal server error occurred while resolving "actions/checkout@v4". Internal server error occurred while resolving "actions/setup-java@v4". Internal server error occurred while resolving "actions/upload-artifact@v3"

Seems there are some issues with GA, need to wait until it's resolved to continue testing.

[LuciferYang]

Example 2: Converting a complex StructType to a CSV string displayed different results between Regular Spark and Spark Connect, skip test it in this pr and add TODO(SPARK-46654):

**********************************************************************
3953File "/__w/spark/spark/python/pyspark/sql/connect/functions/builtin.py", line 2232, in pyspark.sql.connect.functions.builtin.to_csv
3954Failed example:
3955    df.select(sf.to_csv(df.value)).show(truncate=False)
3956Expected:
3957    +-----------------------+
3958    |to_csv(value)          |
3959    +-----------------------+
3960    |2,Alice,"[100,200,300]"|
3961    +-----------------------+
3962Got:
3963    +--------------------------------------------------------------------------+
3964    |to_csv(value)                                                             |
3965    +--------------------------------------------------------------------------+
3966    |2,Alice,org.apache.spark.sql.catalyst.expressions.UnsafeArrayData@99c5e30f|
3967    +--------------------------------------------------------------------------+
3968    <BLANKLINE>
3969**********************************************************************
3970   1 of  18 in pyspark.sql.connect.functions.builtin.to_csv
3971***Test Failed*** 1 failures. 

[LuciferYang]

Python 3.11.1 (v3.11.1:a7a450f84a, Dec  6 2022, 15:24:06) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
Setting default log level to "WARN".
To adjust logging level use sc.setLogLevel(newLevel). For SparkR, use setLogLevel(newLevel).
24/01/10 13:56:18 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
24/01/10 13:56:18 WARN Utils: Service 'SparkUI' could not bind on port 4040. Attempting port 4041.
24/01/10 13:56:18 WARN Utils: Service 'SparkUI' could not bind on port 4041. Attempting port 4042.
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /__ / .__/\_,_/_/ /_/\_\   version 4.0.0-SNAPSHOT
      /_/

Using Python version 3.11.1 (v3.11.1:a7a450f84a, Dec  6 2022 15:24:06)
Spark context Web UI available at http://localhost:4042
Spark context available as 'sc' (master = local[*], app id = local-1704866178807).
SparkSession available as 'spark'.
>>> from pyspark.sql import Row, functions as sf
>>> data = [(1, Row(age=2, name='Alice', scores=[100, 200, 300]))]
>>> df = spark.createDataFrame(data, ("key", "value"))
>>> df.select(sf.to_csv(df.value)).show(truncate=False)
+-----------------------+                                                       
|to_csv(value)          |
+-----------------------+
|2,Alice,"[100,200,300]"|
+-----------------------+

[LuciferYang]

./bin/pyspark --remote "sc://localhost"

Python 3.11.1 (v3.11.1:a7a450f84a, Dec  6 2022, 15:24:06) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /__ / .__/\_,_/_/ /_/\_\   version 4.0.0.dev0
      /_/

Using Python version 3.11.1 (v3.11.1:a7a450f84a, Dec  6 2022 15:24:06)
Client connected to the Spark Connect server at localhost
SparkSession available as 'spark'.
>>> from pyspark.sql import Row, functions as sf
>>> data = [(1, Row(age=2, name='Alice', scores=[100, 200, 300]))]
>>> df = spark.createDataFrame(data, ("key", "value"))
>>> df.select(sf.to_csv(df.value)).show(truncate=False)
+--------------------------------------------------------------------------+
|to_csv(value)                                                             |
+--------------------------------------------------------------------------+
|2,Alice,org.apache.spark.sql.catalyst.expressions.UnsafeArrayData@99c5e30f|
+--------------------------------------------------------------------------+

[LuciferYang]

Merged into master. Thanks @HyukjinKwon