docs: function require (id, parentId) {
      var originalInputId = id; // for "not found" error message
      if (id.charAt(0) === '.') {
        id = normalizeId(id, parentId);
      }
      if (!require.modules.hasOwnProperty(id)) {
        throw new Error('module not found '+JSON.stringify(originalInputId));
      }
      var mod = require.modules[id];
      if (mod.exports === undefined) {
        var _require = function (_id) {
          //console.log('_require', _id, 'from', id);
          return require(_id, id);
        };
        defineConstant(_require, 'main', require.main);
        var block = mod.block; delete mod.block;
        mod.exports = {};
        if (require.initFilter) {
          block = require.initFilter(block);
        }
        block(_require, mod, mod.exports);
      }
      return mod.exports;
    }