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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_canonical_transaction(self, transaction_hash: Hash32) -> BaseTransaction: """ Returns the requested transaction as specified by the transaction hash from the canonical chain. Raises TransactionNotFound if no transaction with the specified hash is found in the main chain. """

        (block_num, index) = self.chaindb.get_transaction_index(transaction_hash)
        VM_class = self.get_vm_class_for_block_number(block_num)

        transaction = self.chaindb.get_transaction_by_index(
            block_num,
            index,
            VM_class.get_transaction_class(),
        )

        if transaction.hash == transaction_hash:
            return transaction
        else:
            raise TransactionNotFound("Found transaction {} instead of {} in block {} at {}".format(
                encode_hex(transaction.hash),
                encode_hex(transaction_hash),
                block_num,
                index,
            ))