@Nullable
  private static PsiMethodCallExpression findAppendCall(PsiForStatement statement) {
    PsiExpressionStatement body = tryCast(ControlFlowUtils.stripBraces(statement.getBody()), PsiExpressionStatement.class);
    if (body == null) return null;
    PsiMethodCallExpression call = tryCast(body.getExpression(), PsiMethodCallExpression.class);
    if (!APPEND.test(call)) return null;
    return call;
  }
@Nullable
  private static PsiMethodCallExpression findAppendCall(PsiForStatement statement)