Adds the given receipt to the provided block header.

        Returns the updated `receipts_root` for updated block header.

def add_receipt(self, block_header: BlockHeader, index_key: int, receipt: Receipt) -> Hash32:
        """
        Adds the given receipt to the provided block header.

        Returns the updated `receipts_root` for updated block header.
        """
        receipt_db = HexaryTrie(db=self.db, root_hash=block_header.receipt_root)
        receipt_db[index_key] = rlp.encode(receipt)
        return receipt_db.root_hash