docstr: Overwrite first three bits in the file
  :param additional_bits: number of bits that were appended to fill last byte
  :return:
code: def _save_information_about_additional_bits(
      self, additional_bits: int
  ):
      """
      Overwrite first three bits in the file
      :param additional_bits: number of bits that were appended to fill last byte
      :return:
      """
      self.file.seek(0)
      first_byte_raw = self.file.read(1)
      self.file.seek(0)
      first_byte = "{0:08b}".format(
          int.from_bytes(first_byte_raw, "big")
      )
      # overwrite first three bits
      first_byte = first_byte[3:]
      first_byte = "{0:03b}".format(additional_bits) + first_byte
  
      self.write_bits(first_byte)
  
imports: from collections import defaultdict, deque
  import heapq
label_desc: Use image node_id 6 for calling the HuffmanWriter obj's underlying member method code with example usage: obj._save_information_about_additional_bits(additional_bits) without return types