replace if statement with function
make class parsing from file into a function
BUGFIX: fix NameError (s/pattern/class_pattern/)
push filtering on class names into pattern
BUGFIX: s/read_classe/read_classes/
make varible names more informative

s/matches/class_names/; s/name/class_name/
rearrange so loop varibles are close to loop
s/classes/class_names/
make prcessing loop only one level deep

by pushing further extracing work into yielder