Option based trading - subscribe function throwing error

[assistuelectronics]

My code is like below

alice = Aliceblue(user_id='',api_key='')
session_id = alice.get_session_id()
alice.get_contract_master("NFO")

symbol_cepe = alice.get_instrument_for_fno(exch="NFO", symbol='NIFTY', expiry_date="2023-01-12", is_fut=False, strike=18000, is_CE=True)

alice.subscribe(symbol_cepe)

Is throwing below error: What wrong I am doing
line 582, in main
alice.subscribe(symbol_cepe)

line 728, in subscribe
scripts=scripts+__instrument.exchange+"|"+str(__instrument.token)+"#"
AttributeError: 'str' object has no attribute 'exchange'