Use local loopback worker from Python expansion services.

sdks/python/apache_beam/transforms/environments.py

@@ -853,6 +853,18 @@ def create_proto(
         payload=beam_runner_api_pb2.AnyOfEnvironmentPayload(
             environments=environments).SerializeToString())
 
+  def __hash__(self):
+    return sum(hash(env) for env in self._environments)
+
+  def __eq__(self, other):
+    return (
+        isinstance(other, AnyOfEnvironment) and
+        set(self._environments) == set(other._environments))
+
+  def to_runner_api(self, context):
+    return self.create_proto(
+        [env.to_runner_api(context) for env in self._environments])
+
 
 class PyPIArtifactRegistry(object):
   _registered_artifacts = set()  # type: Set[Tuple[str, str]]

sdks/python/apache_beam/yaml/yaml_provider.py

@@ -1108,7 +1108,8 @@ def __enter__(self):
             '{{PORT}}',
             '--fully_qualified_name_glob=*',
             '--pickle_library=cloudpickle',
-            '--requirements_file=' + os.path.join(venv + '-requirements.txt')
+            '--requirements_file=' + os.path.join(venv + '-requirements.txt'),
+            '--serve_loopback_worker',
         ])
     self._service = self._service_provider.__enter__()
     return self._service