📝 **Task:** Write `is_anagram(a, b)` returning `True` if strings `a` and `b` are anagrams (same letters, any order), else `False`. Print `is_anagram('listen', 'silent')`. 📋 Implement the function above. Test cases run automatically. 💡 **Hint:** Re-read the theory if you get stuck — the pattern is right there.