Add annotation for services.

PiperOrigin-RevId: 491410618

src/google/protobuf/compiler/python/pyi_generator.cc

diff --git a/src/google/protobuf/compiler/python/pyi_generator.cc b/src/google/protobuf/compiler/python/pyi_generator.cc
index 607a054..67aff2f 100644
--- a/src/google/protobuf/compiler/python/pyi_generator.cc
+++ b/src/google/protobuf/compiler/python/pyi_generator.cc
@@ -564,6 +564,7 @@
         "class $service_name$(_service.service): ...\n\n"
         "class $service_name$_Stub($service_name$): ...\n",
         "service_name", file_->service(i)->name());
+    Annotate("service_name", file_->service(i));
   }
 }