[SPARK-10509][PYSPARK] Reduce excessive param boiler plate code

The current python ml params require cut-and-pasting the param setup and description between the class & ```__init__``` methods. Remove this possible case of errors & simplify use of custom params by adding a ```_copy_new_parent``` method to param so as to avoid cut and pasting (and cut and pasting at different indentation levels urgh).

Author: Holden Karau <holden@us.ibm.com>

Closes #10216 from holdenk/SPARK-10509-excessive-param-boiler-plate-code.

1 files changed, 2 insertions, 2 deletions

diff --git a/python/pyspark/ml/pipeline.py b/python/pyspark/ml/pipeline.py
index 9f5f6ac8fa..661074ca96 100644
--- a/python/pyspark/ml/pipeline.py
+++ b/python/pyspark/ml/pipeline.py
@@ -149,6 +149,8 @@ class Pipeline(Estimator):
     .. versionadded:: 1.3.0
     """
 
+    stages = Param(Params._dummy(), "stages", "pipeline stages")
+
     @keyword_only
     def __init__(self, stages=None):
         """
@@ -157,8 +159,6 @@ class Pipeline(Estimator):
         if stages is None:
             stages = []
         super(Pipeline, self).__init__()
-        #: Param for pipeline stages.
-        self.stages = Param(self, "stages", "pipeline stages")
         kwargs = self.__init__._input_kwargs
         self.setParams(**kwargs)