final void add(IN_NAME name, String... values) {
        final NAME normalizedName = normalizeName(name);
        requireNonNull(values, "values");
        final int h = hashName(normalizedName);
        final int i = index(h);
        for (String v : values) {
            requireNonNullElement(values, v);
            addAndNotify(h, i, normalizedName, v, false);
        }
        onChange(normalizedName);
    }
Validates the given user-specified {@code value}.
core/src/main/java/com/linecorp/armeria/common/StringMultimap.java