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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 retrieve(self, txid, headers=None):
 """Retrieves the transaction with the given id. Args: txid (str):
 Id of the transaction to retrieve. headers (dict):
 Optional headers to pass to the request. Returns: dict: The transaction with the given id. """

        path = self.path + txid
        return self.transport.forward_request(
            method='GET', path=path, headers=None)