code: def _init_file(self):
          
          header_length = 2*SECTOR_LENGTH
          if self.size > header_length:
              self.file.truncate(header_length)
          self.file.seek(0)
          self.file.write(header_length*b'\x00')
          self.size = header_length
docs: Initialise the file header. This will erase any data previously in the file.