docs: protected String getReturnType(ExecutableMethod method) {
          Class returnType = method.getReturnType().getType();
          if (Publishers.isSingle(returnType) || Publishers.isConvertibleToPublisher(returnType)) {
              Argument[] typeParams = method.getReturnType().getTypeParameters();
              if (typeParams.length > 0) {
                  returnType = typeParams[0].getType();
              }
          }
          return returnType.getName();
      }