constructor(config) {
        super();
        this.config = config;
        this.pattern = createPattern(this.config.pattern);
        this.content = this.config.content;
    }
@param {Object} config The configuration options for the pre-tokenizer.
@param {Object} config.pattern The pattern used to split the text. Can be a string or a regex object.
@param {string} config.content What to replace the pattern with.