https://github.com/nipunn1313/mypy-protobuf has not yet been packaged.
It adds typing information to Anki and is only needed for development.

I have packaged some of its test-dependencies on ::guru. Unfortunately,
I'm not too happy yet with the quality of the transitive test-dep
dev-python/pytest-mypy-plugins. Any help is welcome!

From: Lucio Sauer <watermanpaint@posteo.net>
--- a/build/configure/src/python.rs
+++ b/build/configure/src/python.rs
@@ -90,9 +90,7 @@ pub struct GenPythonProto {
 impl BuildAction for GenPythonProto {
     fn command(&self) -> &str {
         "$protoc $
-        --plugin=protoc-gen-mypy=$protoc-gen-mypy $
         --python_out=$builddir/pylib $
-        --mypy_out=$builddir/pylib $
         -Iproto $in"
     }
 
@@ -110,7 +108,6 @@ impl BuildAction for GenPythonProto {
             .collect();
         build.add_inputs("in", &self.proto_files);
         build.add_inputs("protoc", inputs![":protoc_binary"]);
-        build.add_inputs("protoc-gen-mypy", inputs![":pyenv:protoc-gen-mypy"]);
         build.add_outputs("", python_outputs);
     }