def _fromString_PRIVATE_OPENSSH(cls, data, passphrase):
        """
        Return a private key object corresponding to this OpenSSH private key
        string.  If the key is encrypted, passphrase MUST be provided.
        Providing a passphrase for an unencrypted key is an error.

        @type data: L{bytes}
        @param data: The key data.

        @type passphrase: L{bytes} or L{None}
        @param passphrase: The passphrase the key is encrypted with, or L{None}
        if it is not encrypted.

        @return: A new key.
        @rtype: L{twisted.conch.ssh.keys.Key}
        @raises BadKeyError: if
            * a passphrase is provided for an unencrypted key
            * the encoding is incorrect
        @raises EncryptedKeyError: if
            * a passphrase is not provided for an encrypted key
        """
        if data.strip().splitlines()[0][11:-17] == b'OPENSSH':
            # New-format (openssh-key-v1) key
            return cls._fromPrivateOpenSSH_v1(data, passphrase)
        else:
            # Old-format (PEM) key
            return cls._fromPrivateOpenSSH_PEM(data, passphrase)

        Return a private key object corresponding to this OpenSSH private key
        string.  If the key is encrypted, passphrase MUST be provided.
        Providing a passphrase for an unencrypted key is an error.

        @type data: L{bytes}
        @param data: The key data.

        @type passphrase: L{bytes} or L{None}
        @param passphrase: The passphrase the key is encrypted with, or L{None}
        if it is not encrypted.

        @return: A new key.
        @rtype: L{twisted.conch.ssh.keys.Key}
        @raises BadKeyError: if
            * a passphrase is provided for an unencrypted key
            * the encoding is incorrect
        @raises EncryptedKeyError: if
            * a passphrase is not provided for an encrypted key
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/ssh/keys.py