need help for an assignment plz noob here

[pedrorenato1998 at gmail.com]

Hello guys. so my assignment consists in creating a key generator so i can use it in later steps of my work. In my first step i have to write a function called key_generator that receives an argument, letters, that consists in a tuple of 25 caracters. The function returns a tuple of 5 tuples of caracters, each tuple with 5 elements.
 Sounds confusing right? well I have the final product but i dont know how to get there. I was told by my professor that I dont really have to use any complicated knowledge of python so I have to keep it simple. Can u help me plz? just give me a hint how to do it and i'll do everything plz.

example:
Python Shell

>>> letters = (‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’, ‘G’, \
... ‘H’, ‘I’, ‘J’, ‘ ’, ‘L’, ‘M’, ‘N’, \
... ‘O’, ‘P’, ‘Q’, ‘R’, ‘S’, ‘T’, ‘U’, \
... ‘V’, ‘X’, ‘Z’, ‘.’)
>>> key_generator(letters)
... ((‘A’, ‘B’, ‘C’, ‘D’, ‘E’),
... (‘F’, ‘G’, ‘H’, ‘I’, ‘J’),
... (‘ ’, ‘L’, ‘M’, ‘N’, ‘O’),
... (‘P’, ‘Q’, ‘R’, ‘S’, ‘T’),
... (‘U’, ‘V’, ‘X’, ‘Z’, ‘.’))