code: def parse(self, instr):
          '''
          A method to parse ISO hybridization info out of an existing ISO.
          Parameters:
           instr - The data for the ISO hybridization.
          Returns:
           Nothing.
          '''
          if self._initialized:
              raise pycdlibexception.PyCdlibInternalError('This IsoHybrid object is already initialized')
          if len(instr) != 512:
              raise pycdlibexception.PyCdlibInvalidISO('Invalid size of the instr')
          if instr[0:32] == self.ORIG_HEADER:
              self.header = self.ORIG_HEADER
          elif instr[0:32] == self.MAC_AFP:
              self.header = self.MAC_AFP
          else:
              return False
          (self.mbr, self.rba, unused1, self.mbr_id,
           unused2) = struct.unpack_from(self.FMT, instr[:32 + struct.calcsize(self.FMT)], 32)
          if unused1 != 0:
              raise pycdlibexception.PyCdlibInvalidISO('Invalid IsoHybrid section')
          if unused2 != 0:
              raise pycdlibexception.PyCdlibInvalidISO('Invalid IsoHybrid section')
          offset = 32 + struct.calcsize(self.FMT)
          for i in range(1, 5):
              if bytes(bytearray([instr[offset]])) == b'\x80':
                  self.part_entry = i
                  (const_unused, self.bhead, self.bsect, self.bcyle, self.ptype,
                   self.ehead, self.esect, self.ecyle, self.part_offset,
                   self.psize) = struct.unpack_from('=BBBBBBBBLL', instr[:offset + 16], offset)
                  break
              offset += 16
          else:
              raise pycdlibexception.PyCdlibInvalidISO('No valid partition found in IsoHybrid!')
          if bytes(bytearray([instr[-2]])) != b'\x55' or bytes(bytearray([instr[-1]])) != b'\xaa':
              raise pycdlibexception.PyCdlibInvalidISO('Invalid tail on isohybrid section')
          self.geometry_heads = self.ehead + 1
          self.geometry_sectors = 32
          self._initialized = True
          return True