private static @NotNull Map<StubIndexKey<?, ?>, Map<Object, StubIdList>> getStubIndexMaps(@NotNull StubCumulativeInputDiffBuilder diffBuilder) {
    SerializedStubTree tree = diffBuilder.getSerializedStubTree();
    return tree == null ? Collections.emptyMap() : tree.getStubIndicesValueMap();
  }
private static @NotNull Map<StubIndexKey<?, ?>, Map<Object, StubIdList>> getStubIndexMaps(@NotNull StubCumulativeInputDiffBuilder diffBuilder)