docs: def number_of_modified_bytes(buf, fuzzed_buf):
      """Determine the number of differing bytes.
  
      :param buf: original buffer.
      :param fuzzed_buf: fuzzed buffer.
      :return: number of different bytes.
      :rtype: int
      """
      count = 0
      for idx, b in enumerate(buf):
          if b != fuzzed_buf[idx]:
              count += 1
      return count