[SPARK-3309] [PySpark] Put all public API in __all__

Put all public API in __all__, also put them all in pyspark.__init__.py, then we can got all the documents for public API by `pydoc pyspark`. It also can be used by other programs (such as Sphinx or Epydoc) to generate only documents for public APIs.

Author: Davies Liu <davies.liu@gmail.com>

Closes #2205 from davies/public and squashes the following commits:

c6c5567 [Davies Liu] fix message
f7b35be [Davies Liu] put SchemeRDD, Row in pyspark.sql module
7e3016a [Davies Liu] add __all__ in mllib
6281b48 [Davies Liu] fix doc for SchemaRDD
6caab21 [Davies Liu] add public interfaces into pyspark.__init__.py

1 files changed, 5 insertions, 5 deletions

diff --git a/python/pyspark/mllib/regression.py b/python/pyspark/mllib/regression.py
index d8792cf448..f572dcfb84 100644
--- a/python/pyspark/mllib/regression.py
+++ b/python/pyspark/mllib/regression.py
@@ -17,15 +17,15 @@
 
 from numpy import array, ndarray
 from pyspark import SparkContext
-from pyspark.mllib._common import \
-    _dot, _get_unmangled_rdd, _get_unmangled_double_vector_rdd, \
-    _serialize_double_matrix, _deserialize_double_matrix, \
-    _serialize_double_vector, _deserialize_double_vector, \
-    _get_initial_weights, _serialize_rating, _regression_train_wrapper, \
+from pyspark.mllib._common import _dot, _regression_train_wrapper, \
     _linear_predictor_typecheck, _have_scipy, _scipy_issparse
 from pyspark.mllib.linalg import SparseVector, Vectors
 
 
+__all__ = ['LabeledPoint', 'LinearModel', 'LinearRegressionModel', 'RidgeRegressionModel'
+           'LinearRegressionWithSGD', 'LassoWithSGD', 'RidgeRegressionWithSGD']
+
+
 class LabeledPoint(object):
 
     """