The kata defines the following variables that are imported automatically.

bin      = '01'
oct      = '01234567'
dec      = '0123456789'
hex      = '0123456789abcdef'
allow    = 'abcdefghijklmnopqrstuvwxyz'
allup    = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
alpha    = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
alphanum = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

There really isn't any reason why your solution should need these, but it has the unfortunate consequence of shadowing the builtins bin, oct, and hex.

see above, plz