function scopeSugar(mode) {
    if (mode.scope && typeof mode.scope === "object" && mode.scope !== null) {
      mode.beginScope = mode.scope;
      delete mode.scope;
    }
  }
this exists only to allow `scope: {}` to be used beside `match:`
Otherwise `beginScope` would necessary and that would look weird

    {
      match: [ /def/, /\w+/ ]
      scope: { 1: "keyword" , 2: "title" }
    }
@param {CompiledMode} mode