To form a LightClientUpdate, the following historical states and blocks are needed: - state: the post state of any block with a post-Altair parent block - block: the corresponding block - attested_state: the post state of attested_block - attested_block: the block referred to by block.parent_root - finalized_block: the block referred to by attested_state.finalized_checkpoint.root, if locally available (may be unavailable, e.g., when using checkpoint sync, or if it was pruned locally).