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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 identifier(self):
 """Get the identifier for this node. Extended keys can be identified by the Hash160 (RIPEMD160 after SHA256) of the public key's `key`. This corresponds exactly to the data used in traditional Bitcoin addresses. It is not advised to represent this data in base58 format though, as it may be interpreted as an address that way (and wallet software is not required to accept payment to the chain key itself). """

        key = self.get_public_key_hex()
        return ensure_bytes(hexlify(hash160(unhexlify(ensure_bytes(key)))))