code: function _createProxy(ids, workspaces) {
    const _workspaces = makeArray(ids).map(id=>{
      if (!workspaces.has(id)) workspaces.set(id, {});
      return workspaces.get(id);
    });
  
    return new Proxy(global, {
      get: function(target, property, receiver) {
        if (property === 'global') return global;
        for (let n=0; n<_workspaces.length; n++) {
          if (property in _workspaces[n]) return Reflect.get(_workspaces[n], property, receiver);
        }
        return Reflect.get(target, property, receiver);
      },
      has: function(target, property) {
        for (let n=0; n<_workspaces.length; n++) {
          if (property in _workspaces[n]) return true;
        }
        return Reflect.has(target, property);
      },
      set: function(target, property, value, receiver) {
        return Reflect.set(target, property, value, receiver);
      }
    });
  }
docs: Create a Proxy for use a sandbox global.
  
  @private
  @param {Array.<Symbol>} ids        The workspaces to apply to the proxy, in order of use.
  @param {Workspaces} workspaces     The workspaces store.
  @returns {Proxy}                   The created proxy.