Question

I'm learning python using "Think python" the pdf format and currently on chapter 9.3. I'm not understanding how "uses_all" was an instance of a previously-solved problem. The following functions don't give me the same answers if I call them with:
print uses_only('aa', 'aeiou')
print uses_all('aa', 'aeiou')

def uses_only(word, available):
for ltr in word:
if ltr not in available:
return False
return True
def uses_all(word, required):
for ltr in required:
if ltr not in word:
return False
return True
def uses_all(word, required):
return ...