+ * @to_tokens: Serializes a #GIcon into tokens. The tokens must not
+ * contain any whitespace. Don't implement if the #GIcon can't be
+ * serialized (Since 2.20).
+ * @from_tokens: Constructs a #GIcon from tokens. Set the #GError if
+ * the tokens are malformed. Don't implement if the #GIcon can't be
+ * serialized (Since 2.20).