code: def get_catchup_block_ids(self, last_known_block_id):
          '''
          Raises:
              PossibleForkDetectedError
          '''
          # If latest known block is not the current chain head, catch up
          catchup_up_blocks = []
          chain_head = self._block_store.chain_head
          if chain_head and last_known_block_id != chain_head.identifier:
              # Start from the chain head and get blocks until we reach the
              # known block
              for block in self._block_store.get_predecessor_iter():
                  # All the blocks if NULL_BLOCK_IDENTIFIER
                  if last_known_block_id != NULL_BLOCK_IDENTIFIER:
                      if block.identifier == last_known_block_id:
                          break
                  catchup_up_blocks.append(block.identifier)
  
          return list(reversed(catchup_up_blocks)f get_catchup_block_ids(self, last_known_block_id):
          '''
          Raises:
              PossibleForkDetectedError
          '''
          # If latest known block is not the current chain head, catch up
          catchup_up_blocks = []
          chain_head = self._block_store.chain_head
          if chain_head and last_known_block_id != chain_head.identifier:
              # Start from the chain head and get blocks until we reach the
              # known block
              for block in self._block_store.get_predecessor_iter():
                  # All the blocks if NULL_BLOCK_IDENTIFIER
                  if last_known_block_id != NULL_BLOCK_IDENTIFIER:
                      if block.identifier == last_known_block_id:
                          break
                  catchup_up_blocks.append(block.identifier)
  
          return list(reversed(catchup_up_blocks))
docs: Raises:
              PossibleForkDetectedError