public @NotNull Collection<CompilerMessage> getMessages(@NotNull CompilerMessageCategory category) {
    final Collection<CompilerMessage> collection = myMessages.get(category);
    if (collection == null) {
      return Collections.emptyList();
    }
    return Collections.unmodifiableCollection(collection);
  }
public @NotNull Collection<CompilerMessage> getMessages(@NotNull CompilerMessageCategory category)