code: def save(self, folder, format):
          
          try:
              mkdir(folder)
          except Exception:
              pass
          for document in self.documents:
              f = join(folder, document.id)
              content = u"\n".join(document.sentences)
              write(f, content)
docs: save wscorpus to files
  
          :param str folder: path to directory
          :type folder: string
          :param str format: either TEXT or COLUMN
          :type format: str