code: public List<Error> validate(Object target) {
  		DeleteItemRequest instance = (DeleteItemRequest) target;
  		List<Error> errors = ValidatorUtils.invokeValidator(new TableNameValidator(), instance.getTableName());
  		errors.addAll(ValidatorUtils.invokeValidator(new KeyValidator(), instance.getKey()));
  		if (instance.getExpected() != null) {
  			errors.addAll(ValidatorUtils.invokeValidator(new ExpectedValidator(), instance.getExpected()));
  		}
  		if (instance.getReturnValues() != null) {
  			errors.addAll(ValidatorUtils.rejectIfNotMatchRegex(instance.getReturnValues(), "^(NONE|ALL_OLD)$"));
  		}
  		return removeNulls(errors);
  	}
docs: /*
  {"TableName":"Table1",
  "Key":
  {"HashKeyElement":{"S":"AttributeValue1"},"RangeKeyElement":{"N":"AttributeValue2"}},
  "Expected":{"AttributeName3":{"Value":{"S":"AttributeValue3"}}},
  "ReturnValues":"ALL_OLD"}
  }