code: function normalize(id, baseId) {
          if (!id) {
              return '';
          }
  
          baseId = baseId || '';
          var idInfo = parseId(id);
          if (!idInfo) {
              return id;
          }
  
          var resourceId = idInfo.res;
          var moduleId = relative2absolute(idInfo.mod, baseId);
  
          // 根据config中的map配置进行module id mapping
          indexRetrieve(
              baseId,
              mappingIdIndex,
              function (value) {
                  indexRetrieve(
                      moduleId,
                      value,
                      function (mdValue, mdKey) {
                          moduleId = moduleId.replace(mdKey, mdValue);
                      }
                  );
              }
          );
  
          moduleId = resolvePackageId(moduleId);
  
          if (resourceId) {
              var mod = modIs(moduleId, MODULE_DEFINED) && actualGlobalRequire(moduleId);
              resourceId = mod && mod.normalize
                  ? mod.normalize(
                      resourceId,
                      function (resId) {
                          return normalize(resId, baseId);
                      }
                    )
                  : normalize(resourceId, baseId);
  
              moduleId += '!' + resourceId;
          }
  
          return moduleId;
      }
docs: id normalize化
  
  @inner
  @param {string} id 需要normalize的模块标识
  @param {string} baseId 当前环境的模块标识
  @return {string} normalize结果