post_process(tokens, ...args) {
        throw Error("post_process should be implemented in subclass.")
    }
Method to be implemented in subclass to apply post-processing on the given tokens.

@param {Array} tokens The input tokens to be post-processed.
@param {...*} args Additional arguments required by the post-processing logic.
@returns {PostProcessedOutput} The post-processed tokens.
@throws {Error} If the method is not implemented in subclass.