code: def index_collection(self, filenames):
          "Index a whole collection of files."
          for filename in filenames:
              self.index_document(open(filename).read(), filenamef index_collection(self, filenames):
          "Index a whole collection of files."
          for filename in filenames:
              self.index_document(open(filename).read(), filename)
docs: Index a whole collection of files.