[SPARK-18319][ML][QA2.1] 2.1 QA: API: Experimental, DeveloperApi, final, sealed audit

## What changes were proposed in this pull request?
make a pass through the items marked as Experimental or DeveloperApi and see if any are stable enough to be unmarked. Also check for items marked final or sealed to see if they are stable enough to be opened up as APIs.

Some discussions in the jira: https://issues.apache.org/jira/browse/SPARK-18319

## How was this patch tested?
existing ut

Author: Yuhao <yuhao.yang@intel.com>
Author: Yuhao Yang <hhbyyh@gmail.com>

Closes #15972 from hhbyyh/experimental21.

1 files changed, 0 insertions, 8 deletions

diff --git a/python/pyspark/ml/util.py b/python/pyspark/ml/util.py
index bec4b28952..c65b3d14be 100644
--- a/python/pyspark/ml/util.py
+++ b/python/pyspark/ml/util.py
@@ -62,8 +62,6 @@ class Identifiable(object):
 @inherit_doc
 class MLWriter(object):
     """
-    .. note:: Experimental
-
     Utility class that can save ML instances.
 
     .. versionadded:: 2.0.0
@@ -129,8 +127,6 @@ class JavaMLWriter(MLWriter):
 @inherit_doc
 class MLWritable(object):
     """
-    .. note:: Experimental
-
     Mixin for ML instances that provide :py:class:`MLWriter`.
 
     .. versionadded:: 2.0.0
@@ -159,8 +155,6 @@ class JavaMLWritable(MLWritable):
 @inherit_doc
 class MLReader(object):
     """
-    .. note:: Experimental
-
     Utility class that can load ML instances.
 
     .. versionadded:: 2.0.0
@@ -242,8 +236,6 @@ class JavaMLReader(MLReader):
 @inherit_doc
 class MLReadable(object):
     """
-    .. note:: Experimental
-
     Mixin for instances that provide :py:class:`MLReader`.
 
     .. versionadded:: 2.0.0