@Nullable
  private static PsiExpression extractLambdaReturnExpression(PsiLambdaExpression lambda) {
    PsiElement lambdaBody = lambda.getBody();
    PsiExpression expression = null;
    if (lambdaBody instanceof PsiExpression) {
      expression = (PsiExpression)lambdaBody;
    }
    else if (lambdaBody instanceof PsiCodeBlock) {
      PsiStatement[] statements = ((PsiCodeBlock)lambdaBody).getStatements();
      if (statements.length == 1 && statements[0] instanceof PsiReturnStatement) {
        expression = ((PsiReturnStatement)statements[0]).getReturnValue();
      }
    }
    return PsiUtil.skipParenthesizedExprDown(expression);
  }
@Nullable
  private static PsiExpression extractLambdaReturnExpression(PsiLambdaExpression lambda)