[SPARK-3952] [Streaming] [PySpark] add Python examples in Streaming Programming Guide

Having Python examples in Streaming Programming Guide.

Also add RecoverableNetworkWordCount example.

Author: Davies Liu <davies.liu@gmail.com>
Author: Davies Liu <davies@databricks.com>

Closes #2808 from davies/pyguide and squashes the following commits:

8d4bec4 [Davies Liu] update readme
26a7e37 [Davies Liu] fix format
3821c4d [Davies Liu] address comments, add missing file
7e4bb8a [Davies Liu] add Python examples in Streaming Programming Guide

1 files changed, 5 insertions, 3 deletions

diff --git a/python/pyspark/streaming/dstream.py b/python/pyspark/streaming/dstream.py
index 5ae5cf07f0..0826ddc56e 100644
--- a/python/pyspark/streaming/dstream.py
+++ b/python/pyspark/streaming/dstream.py
@@ -441,9 +441,11 @@ class DStream(object):
 
         if `invReduceFunc` is not None, the reduction is done incrementally
         using the old window's reduced value :
-         1. reduce the new values that entered the window (e.g., adding new counts)
-         2. "inverse reduce" the old values that left the window (e.g., subtracting old counts)
-         This is more efficient than `invReduceFunc` is None.
+
+        1. reduce the new values that entered the window (e.g., adding new counts)
+
+        2. "inverse reduce" the old values that left the window (e.g., subtracting old counts)
+        This is more efficient than `invReduceFunc` is None.
 
         @param reduceFunc:     associative reduce function
         @param invReduceFunc:  inverse reduce function of `reduceFunc`