code: def _rm_dr_link(self, rec):
          '''
          An internal method to remove a Directory Record link given the record.
          Parameters:
           rec - The Directory Record to remove.
          Returns:
           The number of bytes to remove from the ISO.
          '''
          if not rec.is_file():
              raise pycdlibexception.PyCdlibInvalidInput('Cannot remove a directory with rm_hard_link (try rm_directory instead)')
          num_bytes_to_remove = 0
          logical_block_size = rec.vd.logical_block_size()
          done = False
          while not done:
              num_bytes_to_remove += self._remove_child_from_dr(rec,
                                                                rec.index_in_parent,
                                                                logical_block_size)
              if rec.inode is not None:
                  found_index = None
                  for index, link in enumerate(rec.inode.linked_records):
                      if id(link) == id(rec):
                          found_index = index
                          break
                  else:
                      raise pycdlibexception.PyCdlibInternalError('Could not find inode corresponding to record')
                  del rec.inode.linked_records[found_index]
                  if not rec.inode.linked_records:
                      found_index = None
                      for index, ino in enumerate(self.inodes):
                          if id(ino) == id(rec.inode):
                              found_index = index
                              break
                      else:
                          raise pycdlibexception.PyCdlibInternalError('Could not find inode corresponding to record')
                      del self.inodes[found_index]
                      num_bytes_to_remove += rec.get_data_length()
              if rec.data_continuation is not None:
                  rec = rec.data_continuation
              else:
                  done = True
          return num_bytes_to_remove