code: def add_receipt(self, block_header: BlockHeader, index_key: int, receipt: Receipt) -> Hash32:
          
          receipt_db = HexaryTrie(db=self.db, root_hash=block_header.receipt_root)
          receipt_db[index_key] = rlp.encode(receipt)
          return receipt_db.root_hash
docs: Adds the given receipt to the provided block header.
  
          Returns the updated `receipts_root` for updated block header.