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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 to_b58check(self, testnet=False):
 """ Generates a Base58Check encoding of this private key. Returns: str: A Base58Check encoded string representing the key. """

        version = self.TESTNET_VERSION if testnet else self.MAINNET_VERSION
        return base58.b58encode_check(bytes([version]) + bytes(self))