code: def _send_chunk(self, chunk, chunk_num):
          
          url_info = self.upload_operations.create_file_chunk_url(self.upload_id, chunk_num, chunk)
          self.upload_operations.send_file_external(url_info, chunk)
docs: Send a single chunk to the remote service.
          :param chunk: bytes data we are uploading
          :param chunk_num: int number associated with this chunk