public static boolean isStringLiteral(@Nullable PyAstStatement stmt) {
    if (stmt instanceof PyAstExpressionStatement) {
      final PyAstExpression expr = ((PyAstExpressionStatement)stmt).getExpression();
      if (expr instanceof PyAstStringLiteralExpression) {
        return true;
      }
    }
    return false;
  }
public static boolean isStringLiteral(@Nullable PyAstStatement stmt)