@Override
        public boolean equals(Object other) {
            if (other == this) return true;
            if ( ! (other instanceof Token)) return false;
            return Objects.equals(this.token, ((Token)other).token);
        }
Returns the token to replace occurrences of this by, which equals token() unless this has a replacement.
linguistics/src/main/java/com/yahoo/language/process/SpecialTokens.java