Factory reset my HTC one m8

I had got the code form the AT&T to unlock my phone  and after punching  the provided code  i was able to use the HTC one m8 with other carrier. Now after two years i want to factory rest my HTC one m8, so will i again require the unlock code after the factory reset is complete or i will not be asked for the unlock code, as the phone had previously been unlocked once.