@Nullable
  private static AuthorsMappingProvider createDefaultAuthorsMappingProvider(@NotNull FileAnnotation annotation) {
    List<VcsFileRevision> revisions = annotation.getRevisions();
    if (revisions == null) return null;

    Map<VcsRevisionNumber, String> authorsMapping = new HashMap<>();
    for (VcsFileRevision revision : revisions) {
      String author = revision.getAuthor();
      if (author != null) authorsMapping.put(revision.getRevisionNumber(), author);
    }

    return () -> authorsMapping;
  }
@Nullable
  private static AuthorsMappingProvider createDefaultAuthorsMappingProvider(@NotNull FileAnnotation annotation)