+str Add Flow contramap.

Signed-off-by: He-Pin <hepin1989@gmail.com>

docs/src/test/scala/docs/stream/operators/flow/ContraMap.scala

@@ -0,0 +1,32 @@
+/*
+ * 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.
+ */
+
+package docs.stream.operators.flow
+
+//#imports
+import org.apache.pekko.NotUsed
+import org.apache.pekko.stream.scaladsl._
+
+//#imports
+
+object ContraMap {
+
+  // #contramap
+  val flow: Flow[Int, Int, NotUsed] = Flow[Int]
+  val newFlow: Flow[String, Int, NotUsed] = flow.contramap(_.toInt)
+  // #contramap
+}