Assistant: 
User: 
    Please analyze the following code file and determine whether it belongs to any of the provided modules based on the listed module descriptions.
    Note that the provided list of modules may not be exhaustive, and some files may not belong to any of the modules. 
    If the code belongs to a module, Only output the module name, without any explanation or additional information; otherwise, return 'None' if it does not belong to any module.

    Modules : {
        "UI": "Handles the front-end user interface, consisting of HTML, CSS, and JavaScript files generated by the Angular framework. It processes user requests and interacts with the server using AJAX for data retrieval and client-side interactions."
"Test Driver": "Facilitates automated regression testing and handles transmission of test data in JSON format. It performs Java testing using TestNG and JavaScript unit-testing with Jest. It also sets up a simulated web server for servlet-level tests and automates end-to-end testing using Selenium Java."
"Logic": "Manages the business logic of TEAMMATES, including handling relationships between entities, managing transactions, input value sanitization, access control rights, and interfacing with GAE-provided or third-party APIs."
"Storage": "Performs CRUD operations on data entities, validation of data, and abstraction of GQL queries, hiding the complexities of datastore from the Logic component."
"Common": "Contains utility classes, custom exceptions, and data transfer objects used across the entire application for easy consolidation and transfer of structured data."
"E2E": "Handles end-to-end testing and load & performance testing, providing helpers, abstractions of browser pages, and test cases for E2E tests and L&P tests."
"Client": "Contains scripts for administrative tasks, such as migrating data to a new schema and calculating statistics. This module connects directly to the application back-end for administrative purposes."
    }

    Code: package teammates.common.util; /** * Holds String-related helper functions. */ public final class StringHelper { private static final Logger log = Logger.getLogger(); private StringHelper() { // utility class } /** * Checks whether the input string is empty or equals {@code null}. * @param s The string to be checked */ public static boolean isEmpty(String s) { return s == null || s.isEmpty(); } /** * Generates a string which consists of {@code length} copies of {@code character} without space. */ static String generateStringOfLength(int length, char character) { assert length >= 0; return String.join("", Collections.nCopies(length, String.valueOf(character))); } /** * Checks whether the input string matches the regex. * @param input The string to be matched * @param regex The regex used for the matching */ public static boolean isMatching(String input, String regex) { // Important to use the CANON_EQ flag to make sure that canonical characters // such as é is correctly matched regardless of single/double code point encoding return Pattern.compile(regex, Pattern.CANON_EQ).matcher(input).matches(); } /** * Generates a left-indentation of {@code length} units. */ public static String getIndent(int length) { return generateStringOfLength(length, ' '); } /** * Trims head of the String if it is longer than specified Length. * E.g., String "12345678" with maximumStringLength = 6, returns "345678" * @param maximumStringLength - maximum required length of the string * @return String with at most maximumStringLength length */ public static String truncateHead(String inputString, int maximumStringLength) { int inputStringLength = inputString.length(); if (inputStringLength <= maximumStringLength) { return inputString; } return inputString.substring(inputStringLength - maximumStringLength); } /** * Generates the HMAC SHA-1 signature for a supplied string. * * @param data The string to be signed * @return The signature value as a hex-string */ public static String generateSignature(String data) { try { SecretKeySpec signingKey = new SecretKeySpec(hexStringToByteArray(Config.ENCRYPTION_KEY), "HmacSHA1"); Mac mac = Mac.getInstance("HmacSHA1"); mac.init(signingKey); byte[] value = mac.doFinal(data.getBytes(Const.ENCODING)); return byteArrayToHexString(value); } catch (Exception e) { assert false; return null; } } /** * Verifies the HMAC SHA-1 signature against a given value. * * @param value The value to be checked * @param signature The signature in hex-string format * @return True if signature matches value */ public static boolean isCorrectSignature(String value, String signature) { if (value == null || signature == null) { return false; } return Objects.equals(generateSignature(value), signature); } /** * Encrypts the supplied string. * * @param value the plaintext as a string * @return the ciphertext * @throws RuntimeException if the encryption fails for some reason, such
Assistant: