diff --git a/examples/src/main/python/ml/simple_text_classification_pipeline.py b/examples/src/main/python/ml/simple_text_classification_pipeline.py
index f5558eaebe005..d303d4d97de79 100644
--- a/examples/src/main/python/ml/simple_text_classification_pipeline.py
+++ b/examples/src/main/python/ml/simple_text_classification_pipeline.py
@@ -1,3 +1,20 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
 from pyspark import SparkContext
 from pyspark.sql import SQLContext, Row
 from pyspark.ml import Pipeline
@@ -8,7 +25,10 @@
     sc = SparkContext(appName="SimpleTextClassificationPipeline")
     sqlCtx = SQLContext(sc)
     training = sqlCtx.inferSchema(
-        sc.parallelize([(0L, "a b c d e spark", 1.0), (1L, "b d", 0.0), (2L, "spark f g h", 1.0), (3L, "hadoop mapreduce", 0.0)]) \
+        sc.parallelize([(0L, "a b c d e spark", 1.0),
+                        (1L, "b d", 0.0),
+                        (2L, "spark f g h", 1.0),
+                        (3L, "hadoop mapreduce", 0.0)]) \
           .map(lambda x: Row(id=x[0], text=x[1], label=x[2])))
 
     tokenizer = Tokenizer() \
@@ -26,7 +46,10 @@
     model = pipeline.fit(training)
 
     test = sqlCtx.inferSchema(
-        sc.parallelize([(4L, "spark i j k"), (5L, "l m n"), (6L, "mapreduce spark"), (7L, "apache hadoop")]) \
+        sc.parallelize([(4L, "spark i j k"),
+                        (5L, "l m n"),
+                        (6L, "mapreduce spark"),
+                        (7L, "apache hadoop")]) \
           .map(lambda x: Row(id=x[0], text=x[1])))
 
     for row in model.transform(test).collect():
diff --git a/python/pyspark/ml/__init__.py b/python/pyspark/ml/__init__.py
index b6606c76063db..df39515d81433 100644
--- a/python/pyspark/ml/__init__.py
+++ b/python/pyspark/ml/__init__.py
@@ -18,7 +18,7 @@
 from abc import ABCMeta, abstractmethod
 
 from pyspark import SparkContext
-from pyspark.sql import inherit_doc
+from pyspark.sql import inherit_doc # TODO: move inherit_doc to Spark Core
 from pyspark.ml.param import Param, Params
 from pyspark.ml.util import Identifiable
 
@@ -37,7 +37,7 @@ class PipelineStage(Params):
     """
 
     def __init__(self):
-        super.__init__(self)
+        super(PipelineStage, self).__init__()
 
 
 @inherit_doc
@@ -49,7 +49,7 @@ class Estimator(PipelineStage):
     __metaclass__ = ABCMeta
 
     def __init__(self):
-        super.__init__(self)
+        super(Estimator, self).__init__()
 
     @abstractmethod
     def fit(self, dataset, params={}):
@@ -74,6 +74,9 @@ class Transformer(PipelineStage):
 
     __metaclass__ = ABCMeta
 
+    def __init__(self):
+        super(Transformer, self).__init__()
+
     @abstractmethod
     def transform(self, dataset, params={}):
         """
@@ -109,7 +112,7 @@ class Pipeline(Estimator):
     """
 
     def __init__(self):
-        super.__init__(self)
+        super(Pipeline, self).__init__()
         #: Param for pipeline stages.
         self.stages = Param(self, "stages", "pipeline stages")
 
@@ -139,6 +142,9 @@ def fit(self, dataset):
                 model = stage.fit(dataset)
                 transformers.append(model)
                 dataset = model.transform(dataset)
+            else:
+                raise ValueError(
+                    "Cannot recognize a pipeline stage of type %s." % type(stage).__name__)
         return PipelineModel(transformers)
 
 
@@ -146,6 +152,7 @@ def fit(self, dataset):
 class PipelineModel(Transformer):
 
     def __init__(self, transformers):
+        super(PipelineModel, self).__init__()
         self.transformers = transformers
 
     def transform(self, dataset):
diff --git a/python/pyspark/ml/feature.py b/python/pyspark/ml/feature.py
index ce45105ba2b28..35f32f513f7a5 100644
--- a/python/pyspark/ml/feature.py
+++ b/python/pyspark/ml/feature.py
@@ -16,13 +16,13 @@
 #
 
 from pyspark.sql import SchemaRDD, ArrayType, StringType
-from pyspark.ml import _jvm
+from pyspark.ml import Transformer, _jvm
 from pyspark.ml.param import Param
 
-
-class Tokenizer(object):
+class Tokenizer(Transformer):
 
     def __init__(self):
+        super(Tokenizer, self).__init__()
         self.inputCol = Param(self, "inputCol", "input column name", None)
         self.outputCol = Param(self, "outputCol", "output column name", None)
         self.paramMap = {}
@@ -61,9 +61,10 @@ def transform(self, dataset, params={}):
             raise ValueError("The input params must be either a dict or a list.")
 
 
-class HashingTF(object):
+class HashingTF(Transformer):
 
     def __init__(self):
+        super(HashingTF, self).__init__()
         self._java_obj = _jvm().org.apache.spark.ml.feature.HashingTF()
         self.numFeatures = Param(self, "numFeatures", "number of features", 1 << 18)
         self.inputCol = Param(self, "inputCol", "input column name")
diff --git a/python/pyspark/ml/param.py b/python/pyspark/ml/param.py
index 427a70cc11d5c..ffe58a6ee69d7 100644
--- a/python/pyspark/ml/param.py
+++ b/python/pyspark/ml/param.py
@@ -15,7 +15,7 @@
 # limitations under the License.
 #
 
-from abc import ABCMeta, abstractmethod
+from abc import ABCMeta
 
 from pyspark.ml.util import Identifiable
 
@@ -50,11 +50,10 @@ class Params(Identifiable):
     __metaclass__ = ABCMeta
 
     def __init__(self):
-        super.__init__(self)
+        super(Params, self).__init__()
         #: Internal param map.
         self.paramMap = {}
 
-    @abstractmethod
     def params(self):
         """
         Returns all params. The default implementation uses
diff --git a/python/pyspark/ml/util.py b/python/pyspark/ml/util.py
index c6561a13a5d9d..801a5eeaa3249 100644
--- a/python/pyspark/ml/util.py
+++ b/python/pyspark/ml/util.py
@@ -15,6 +15,8 @@
 # limitations under the License.
 #
 
+import uuid
+
 
 class Identifiable(object):
     """