constructor(utils, i18n) {
        this.utils = utils;
        this.i18n = i18n;
        this.diagramModeFlag = "custom_diagram";  // can be any value, just a flag
        this.panel = `<div class="md-diagram-panel md-fences-adv-panel"><div class="md-diagram-panel-header"></div><div class="md-diagram-panel-preview"></div><div class="md-diagram-panel-error"></div></div>`;
        this.exitInteractiveStrategies = ["click_exit_button"];
        this.parsers = new Map();     // {lang: parser}
        this.langMapping = new Map(); // {lang: mappingLang}
        // this.pending = new Set();     // cid
        // this.timeout = 300;
    }
Dynamically register and unregister new code block diagram.