old_contents: from struct import unpack
  
  class KaitaiStruct:
    def read_u1(self):
      return unpack('B', self._io.read(1))[0]
  
new_contents: from struct import unpack
  
  class KaitaiStruct:
      def close(self):
          self._io.close()
  
      def read_u1(self):
          return unpack('B', self._io.read(1))[0]
  
subject: Fix formatting as per PEP8