2. The parties in this case belong to private lending relationship. The law does not clearly stipulate the contract form of private lending. In reality, private lending often appears in the form of IOUs or IOUs, and the law does not strictly stipulate the form of IOUs or IOUs. Therefore, IOUs or IOUs are valid as long as they are not illegal. Only the signature in the IOU is written by the borrower himself, and all other contents are written by the lender, which does not violate the law. So such an iou is valid.