code: def writeMasterChecksum(self, directory):
      checksumadjustment = self._calcMasterChecksum(directory)
      # write the checksum to the file
      self.file.seek(self.tables["head"].offset + 8)
      self.file.write(struct.pack(">L", checksumadjustment))
  
imports: from io import BytesIO
  from types import SimpleNamespace
  from fontTools.misc.textTools import Tag
  from fontTools.misc import sstruct
  from fontTools.ttLib import TTLibError, TTLibFileIsCollectionError
  import struct
  from collections import OrderedDict
  import logging
label_desc: Use image node_id 8 for calling the SFNTWriter obj's underlying member method code with example usage: obj.writeMasterChecksum(directory) without return types