code: def get_transaction_index(self, transaction_hash: Hash32) -> Tuple[BlockNumber, int]:
          
          key = SchemaV1.make_transaction_hash_to_block_lookup_key(transaction_hash)
          try:
              encoded_key = self.db[key]
          except KeyError:
              raise TransactionNotFound(
                  "Transaction {} not found in canonical chain".format(encode_hex(transaction_hash)))
  
          transaction_key = rlp.decode(encoded_key, sedes=TransactionKey)
          return (transaction_key.block_number, transaction_key.index)
docs: Returns a 2-tuple of (block_number, transaction_index) indicating which
          block the given transaction can be found in and at what index in the
          block transactions.
  
          Raises TransactionNotFound if the transaction_hash is not found in the
          canonical chain.