Sets a record in the database to allow looking up this header by its
        block number.

def _add_block_number_to_hash_lookup(db: BaseDB, header: BlockHeader) -> None:
        """
        Sets a record in the database to allow looking up this header by its
        block number.
        """
        block_number_to_hash_key = SchemaV1.make_block_number_to_hash_lookup_key(
            header.block_number
        )
        db.set(
            block_number_to_hash_key,
            rlp.encode(header.hash, sedes=rlp.sedes.binary),
        )