docs: private Set<Class<?>> wrapperTypesUsedInCollections(ExecutableElement method) {
      TypeElement javaUtilCollection = elementUtils.getTypeElement(Collection.class.getName());
      ImmutableSet.Builder<Class<?>> usedInCollections = ImmutableSet.builder();
      for (Class<?> wrapper : Primitives.allWrapperTypes()) {
        DeclaredType collectionOfWrapper =
            typeUtils.getDeclaredType(javaUtilCollection, getTypeMirror(wrapper));
        for (VariableElement parameter : method.getParameters()) {
          if (typeUtils.isAssignable(parameter.asType(), collectionOfWrapper)) {
            usedInCollections.add(wrapper);
            break;
          }
        }
      }
      return usedInCollections.build();
    }