Create py.typed for use with mypy

CHANGES.md

@@ -68,6 +68,7 @@
 
 * In Python, [RunInference](https://beam.apache.org/documentation/sdks/python-machine-learning/#why-use-the-runinference-api) now supports loading many models in the same transform using a [KeyedModelHandler](https://beam.apache.org/documentation/sdks/python-machine-learning/#use-a-keyed-modelhandler) ([#27628](https://github.com/apache/beam/issues/27628)).
 * In Python, the [VertexAIModelHandlerJSON](https://beam.apache.org/releases/pydoc/current/apache_beam.ml.inference.vertex_ai_inference.html#apache_beam.ml.inference.vertex_ai_inference.VertexAIModelHandlerJSON) now supports passing in inference_args. These will be passed through to the Vertex endpoint as parameters.
+* Added support to run `mypy` on user pipelines ([#27906](https://github.com/apache/beam/issues/27906))
 
 ## Breaking Changes
 

sdks/python/apache_beam/py.typed

@@ -0,0 +1,19 @@
+#
+# 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.
+#
+
+# Marker file for PEP 561.
+# The apache-beam package uses inline types.