code: def count_chunks(self, bytes_per_chunk):
          
          chunks = math.ceil(float(self.size) / float(bytes_per_chunk))
          return max(chunks, 1)
docs: Based on the size of the file determine how many chunks we will need to upload.
          For empty files 1 chunk is returned (DukeDS requires an empty chunk for empty files).
          :param bytes_per_chunk: int: how many bytes should chunks to spglit the file into
          :return: int: number of chunks that will need to be sent