def __init__(self, key=None):
        ''' If the key is not specified a random key will be generated.
        @param key: bytes
        '''
        if key is None:
            key = os.urandom(24)
        self._key = key
def __init__ ( self , key = None ) : if key is None : key = os . urandom ( 24 ) self . _key = key
If the key is not specified a random key will be generated.
        @param key: bytes