[FLINK-28237][python][ml] Improve flink ml python examples in doc

HuangXingBo · HuangXingBo · commit 58dbc3813e37 · 2022-06-27T11:53:27.000+08:00
This closes apache#116.
diff --git a/docs/content/docs/operators/classification/knn.md b/docs/content/docs/operators/classification/knn.md
@@ -121,6 +121,7 @@ output.execute().print();
 {{< tab "Python">}}
 ```python
 from pyflink.common import Types
+from pyflink.datastream import StreamExecutionEnvironment
 from pyflink.table import StreamTableEnvironment
 
 from pyflink.ml.core.linalg import Vectors, DenseVectorTypeInfo
diff --git a/docs/content/docs/operators/classification/logisticregression.md b/docs/content/docs/operators/classification/logisticregression.md
@@ -112,6 +112,7 @@ output.execute().print();
 {{< tab "Python">}}
 ```python
 from pyflink.common import Types
+from pyflink.datastream import StreamExecutionEnvironment
 from pyflink.table import StreamTableEnvironment
 
 from pyflink.ml.core.linalg import Vectors, DenseVectorTypeInfo
diff --git a/docs/content/docs/operators/classification/naivebayes.md b/docs/content/docs/operators/classification/naivebayes.md
@@ -104,6 +104,7 @@ outputTable.execute().print();
 {{< tab "Python">}}
 ```python
 from pyflink.common import Types
+from pyflink.datastream import StreamExecutionEnvironment
 from pyflink.table import StreamTableEnvironment
 
 from pyflink.ml.core.linalg import Vectors, DenseVectorTypeInfo
diff --git a/docs/content/docs/operators/clustering/kmeans.md b/docs/content/docs/operators/clustering/kmeans.md
@@ -104,6 +104,7 @@ for (CloseableIterator<Row> it = output.execute().collect(); it.hasNext(); ) {
 {{< tab "Python">}}
 ```python
 from pyflink.common import Types
+from pyflink.datastream import StreamExecutionEnvironment
 from pyflink.table import StreamTableEnvironment
 
 from pyflink.ml.core.linalg import Vectors, DenseVectorTypeInfo
diff --git a/docs/content/docs/operators/feature/onehotencoder.md b/docs/content/docs/operators/feature/onehotencoder.md
@@ -82,6 +82,7 @@ outputTable.execute().print();
 {{< tab "Python">}}
 ```python
 from pyflink.common import Types, Row
+from pyflink.datastream import StreamExecutionEnvironment
 from pyflink.table import StreamTableEnvironment, Table, DataTypes
 
 from pyflink.ml.lib.feature.onehotencoder import OneHotEncoder, OneHotEncoderModel
