@Nullable
  default <T extends PyAstElement> T childToPsi(TokenSet filterSet, int index) {
    final ASTNode[] nodes = getNode().getChildren(filterSet);
    if (nodes.length <= index) {
      return null;
    }
    //noinspection unchecked
    return (T)nodes[index].getPsi();
  }
@Nullable
  default <T extends PyAstElement> T childToPsi(TokenSet filterSet, int index)