code: function(System, Promise, files, importRegexps, strictImportSequence) {
        if (strictImportSequence) {
          return adapter.sequentialImportFiles(System, Promise, files, importRegexps)
        } else {
          return adapter.parallelImportFiles(System, Promise, files, importRegexps)
        }
      }
docs: Calls System.import on all the files that match one of the importPatterns.
  Returns a single promise which resolves once all imports are complete.
  @param System {object}
  @param Promise {object}
  @param files {object} key/value map of filePaths to change counters
  @param importRegexps {RegExp[]}
  @param [strictImportSequence=false] {boolean} If true, System.import calls are chained to preserve sequence.
  @returns {promise}