PLEASE HELP ME FIX THESE CODES FOR THISnum $=$ None

# FIXME: Decrypt the integer that corresponds to the current

# encrypted letter using the decryption function for an affine

# transformation with key $(a,b)$ so that letter$\_$digits holds

# the decrypted number as a string of two digits

letter$\_$digits $=$ 'None'

if len$($letter$\_$digits$)==1$ :

# FIXME: If the letter number is between $-9,$ inclusive,

# prepend the string with $a_0$

letter$\_$digits $=$ None

# FIXME: Use

util.py to append to the text the decrypted

# Letter corresponding to the current letter digits

text $+=$ 'None'

return text