String fieldName,
            ModelProblemCollector problems,
            Severity severity,
            Version version,
            String string,
            String sourceHint,
            InputLocationTracker tracker) {
        if (string == null || string.isEmpty()) {
            return true;
        }

        if ("true".equalsIgnoreCase(string) || "false".equalsIgnoreCase(string)) {

    public static final String SAME_ORIGIN = "same-origin";
    public static final String ORIGIN = "origin";
    public static final String STRICT_ORIGIN = "strict-origin";
    public static final String ORIGIN_WHEN_CROSS_ORIGIN = "origin-when-cross-origin";
    public static final String STRICT_ORIGIN_WHEN_CROSS_ORIGIN = "strict-origin-when-cross-origin";
    public static final String UNSAFE_URL = "unsafe-url";
  }

  /**

        fun foo() {}

        val bar: String = "bar"

        val bool: Boolean = true

        val isBool: Boolean = true

        var bazar = "bazar"

        var bazool: Boolean = true

        var isFool: Boolean = true

        fun String.fooExt() {}

        fun Int.fooExt() {}

        val String.barExt: String
            get() = "bar"

        var Int.bazarExt: String

		name     string
		metadata map[string]string
		keys     []string
		want     map[string]string
	}{
		{
			name:     "1",
			metadata: map[string]string{"content-type": "application/octet-stream", "etag": "de75a98baf2c6aef435b57dd0fc33c86", "x-amz-storage-class": "STANDARD", "md5": "abcde"},
			keys:     []string{"etag", "md5"},
			want:     map[string]string{"content-type": "application/octet-stream", "x-amz-storage-class": "STANDARD"},

    public static class ApiSystemInfoResponse extends ApiResponse {
        protected List<Map<String, String>> envProps;
        protected List<Map<String, String>> systemProps;
        protected List<Map<String, String>> fessProps;
        protected List<Map<String, String>> bugReportProps;

        public ApiSystemInfoResponse envProps(final List<Map<String, String>> envProps) {
            this.envProps = envProps;
            return this;

    EntryTransformer<String, Integer, String> transformer =
        new EntryTransformer<String, Integer, String>() {
          @Override
          public String transformEntry(String key, Integer value) {
            return key + value;
          }
        };
    ListMultimap<String, String> transformed = Multimaps.transformEntries(multimap, transformer);

   */
  static String nullToEmpty(@CheckForNull String string) {
    return (string == null) ? "" : string;
  }

  /**
   * Returns the string if it is not empty, or a null string otherwise.
   *
   * @param string the string to test and possibly return
   * @return {@code string} if it is not empty; {@code null} otherwise
   */
  @CheckForNull
  static String emptyToNull(@CheckForNull String string) {

    }

    private Map<String, String[]> getResultDocIdsCache(final HttpSession session) {
        @SuppressWarnings("unchecked")
        Map<String, String[]> resultDocIdsCache = (Map<String, String[]>) session.getAttribute(Constants.RESULT_DOC_ID_CACHE);
        if (resultDocIdsCache == null) {
            resultDocIdsCache = new LruHashMap<>(resultDocIdsCacheSize);

			Description:    tierRequestsSuccessMD,
			Value:          float64(stat.success),
			VariableLabels: map[string]string{"tier": tier},
		})
		metrics = append(metrics, MetricV2{
			Description:    tierRequestsFailureMD,
			Value:          float64(stat.failure),
			VariableLabels: map[string]string{"tier": tier},
		})
	}
	return metrics
}

func (config *TierConfigMgr) refreshedAt() time.Time {

          <version>1.0.0+</version>
          <description>Name of the plugin.</description>
          <type>String</type>
        </field>
        <field>
          <name>description</name>
          <version>1.0.0+</version>
          <description>Description of the plugin.</description>
          <type>String</type>
        </field>
        <field>
          <name>groupId</name>
          <version>1.0.0+</version>