@Nullable
    @Override
    public Boolean getBoolean(IN_NAME name) {
        final String v = get(name);
        if (v == null) {
            return null;
        }
        return toBooleanOrNull(v);
    }
Validates the given user-specified {@code value}.
core/src/main/java/com/linecorp/armeria/common/StringMultimap.java