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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 privatekey_to_publickey(private_key_bin: bytes) -> bytes: """ Returns public key in bitcoins 'bin' encoding. """

    if not ishash(private_key_bin):
        raise ValueError('private_key_bin format mismatch. maybe hex encoded?')
    return keys.PrivateKey(private_key_bin).public_key.to_bytes()