[SPARK-13949][ML][PYTHON] PySpark ml DecisionTreeClassifier, Regressor support export/import

[GayathriMurali]

What changes were proposed in this pull request?

Added MLReadable and MLWritable to Decision Tree Classifier and Regressor. Added doctests.

How was this patch tested?

Python Unit tests. Tests added to check persistence in DecisionTreeClassifier and DecisionTreeRegressor.

[GayathriMurali]

@jkbradley Can you please review this patch?

[jkbradley]

Yes, I'll take a look now

[jkbradley]

ok to test

[jkbradley]

LGTM pending tests

Could you please fix the PR title to include the ML and Python tags: "[SPARK-13949][ML][PYTHON] ..."? Thanks!

[SparkQA]

Test build #2670 has finished for PR 11892 at commit 0154444.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • class DecisionTreeClassificationModel(DecisionTreeModel, MLWritable, MLReadable):
  • class DecisionTreeModel(JavaModel, MLWritable, MLReadable):

[jkbradley]

Oops, I didn't spot this. This class should be left alone, and DecisionTreeRegressionModel can be modified instead.

[jkbradley]

OH! I think another issue is a PR which was merged yesterday which conflicts (silently) with this PR. Can you please merge with master?

[GayathriMurali]

@jkbradley This test is not starting automatically. Can you please issue the ok to test again?

[jkbradley]

add to whitelist

[SparkQA]

Test build #2675 has finished for PR 11892 at commit bad5c3e.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[mengxr]

Merged into master. Thanks!