[SPARK-16772] Correct API doc references to PySpark classes + formatting fixes

## What's Been Changed

The PR corrects several broken or missing class references in the Python API docs. It also correct formatting problems.

For example, you can see [here](http://spark.apache.org/docs/2.0.0/api/python/pyspark.sql.html#pyspark.sql.SQLContext.registerFunction) how Sphinx is not picking up the reference to `DataType`. That's because the reference is relative to the current module, whereas `DataType` is in a different module.

You can also see [here](http://spark.apache.org/docs/2.0.0/api/python/pyspark.sql.html#pyspark.sql.SQLContext.createDataFrame) how the formatting for byte, tinyint, and so on is italic instead of monospace. That's because in ReST single backticks just make things italic, unlike in Markdown.

## Testing

I tested this PR by [building the Python docs](https://github.com/apache/spark/tree/master/docs#generating-the-documentation-html) and reviewing the results locally in my browser. I confirmed that the broken or missing class references were resolved, and that the formatting was corrected.

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #14393 from nchammas/python-docstring-fixes.

1 files changed, 4 insertions, 4 deletions

diff --git a/python/pyspark/sql/streaming.py b/python/pyspark/sql/streaming.py
index 8bac347e13..a364555003 100644
--- a/python/pyspark/sql/streaming.py
+++ b/python/pyspark/sql/streaming.py
@@ -269,7 +269,7 @@ class DataStreamReader(OptionUtils):
 
         .. note:: Experimental.
 
-        :param schema: a StructType object
+        :param schema: a :class:`pyspark.sql.types.StructType` object
 
         >>> s = spark.readStream.schema(sdf_schema)
         """
@@ -310,7 +310,7 @@ class DataStreamReader(OptionUtils):
 
         :param path: optional string for file-system backed data sources.
         :param format: optional string for format of the data source. Default to 'parquet'.
-        :param schema: optional :class:`StructType` for the input schema.
+        :param schema: optional :class:`pyspark.sql.types.StructType` for the input schema.
         :param options: all other string options
 
         >>> json_sdf = spark.readStream.format("json")\
@@ -349,7 +349,7 @@ class DataStreamReader(OptionUtils):
 
         :param path: string represents path to the JSON dataset,
                      or RDD of Strings storing JSON objects.
-        :param schema: an optional :class:`StructType` for the input schema.
+        :param schema: an optional :class:`pyspark.sql.types.StructType` for the input schema.
         :param primitivesAsString: infers all primitive values as a string type. If None is set,
                                    it uses the default value, ``false``.
         :param prefersDecimal: infers all floating-point values as a decimal type. If the values
@@ -461,7 +461,7 @@ class DataStreamReader(OptionUtils):
         .. note:: Experimental.
 
         :param path: string, or list of strings, for input path(s).
-        :param schema: an optional :class:`StructType` for the input schema.
+        :param schema: an optional :class:`pyspark.sql.types.StructType` for the input schema.
         :param sep: sets the single character as a separator for each field and value.
                     If None is set, it uses the default value, ``,``.
         :param encoding: decodes the CSV files by the given encoding type. If None is set,