code: def close(self):
          
          index_present = self.contains('index.html')
          self.zf.close() # Make sure zipfile closes no matter what
          if not index_present:
              raise ReferenceError("Invalid Zip at {}: missing index.html file (use write_index_contents method)".format(self.write_to_path))
docs: close: Close zipfile when done
              Args: None
              Returns: None