code: func isTypeApplicableToProtobuf(t *types.Type) bool {
  	// skip functions -- we don't care about them for protobuf
  	if t.Kind == types.Func || (t.Kind == types.DeclarationOf && t.Underlying.Kind == types.Func) {
  		return false
  	}
  	// skip private types
  	if namer.IsPrivateGoName(t.Name.Name) {
  		return false
  	}
  
  	return true
  }
docs: // isTypeApplicableToProtobuf checks to see if a type is relevant for protobuf processing.
  // Currently, it filters out functions and private types.