[SPARK-13430][PYSPARK][ML] Python API for training summaries of linear and logistic regression

## What changes were proposed in this pull request?

Adding Python API for training summaries of LogisticRegression and LinearRegression in PySpark ML.

## How was this patch tested?
Added unit tests to exercise the api calls for the summary classes.  Also, manually verified values are expected and match those from Scala directly.

Author: Bryan Cutler <cutlerb@gmail.com>

Closes #11621 from BryanCutler/pyspark-ml-summary-SPARK-13430.

1 files changed, 23 insertions, 7 deletions

diff --git a/python/pyspark/ml/wrapper.py b/python/pyspark/ml/wrapper.py
index ca93bf7d7d..a2cf2296fb 100644
--- a/python/pyspark/ml/wrapper.py
+++ b/python/pyspark/ml/wrapper.py
@@ -213,8 +213,30 @@ class JavaTransformer(Transformer, JavaWrapper):
         return DataFrame(self._java_obj.transform(dataset._jdf), dataset.sql_ctx)
 
 
+class JavaCallable(object):
+    """
+    Wrapper for a plain object in JVM to make Java calls, can be used
+    as a mixin to another class that defines a _java_obj wrapper
+    """
+    def __init__(self, java_obj=None, sc=None):
+        super(JavaCallable, self).__init__()
+        self._sc = sc if sc is not None else SparkContext._active_spark_context
+        # if this class is a mixin and _java_obj is already defined then don't initialize
+        if java_obj is not None or not hasattr(self, "_java_obj"):
+            self._java_obj = java_obj
+
+    def __del__(self):
+        if self._java_obj is not None:
+            self._sc._gateway.detach(self._java_obj)
+
+    def _call_java(self, name, *args):
+        m = getattr(self._java_obj, name)
+        java_args = [_py2java(self._sc, arg) for arg in args]
+        return _java2py(self._sc, m(*java_args))
+
+
 @inherit_doc
-class JavaModel(Model, JavaTransformer):
+class JavaModel(Model, JavaCallable, JavaTransformer):
     """
     Base class for :py:class:`Model`s that wrap Java/Scala
     implementations. Subclasses should inherit this class before
@@ -259,9 +281,3 @@ class JavaModel(Model, JavaTransformer):
             that._java_obj = self._java_obj.copy(self._empty_java_param_map())
             that._transfer_params_to_java()
         return that
-
-    def _call_java(self, name, *args):
-        m = getattr(self._java_obj, name)
-        sc = SparkContext._active_spark_context
-        java_args = [_py2java(sc, arg) for arg in args]
-        return _java2py(sc, m(*java_args))