def is_anagram_v1(string1, string2):
    """Returns True if both strings are anagrams."""
    letters1 = list(string1.lower())
    letters2 = list(string2.lower())
    letters1.sort()
    letters2.sort()
    return letters1 == letters2


def is_anagram_v2(string1, string2):
    """Returns True if both strings are anagrams."""
    letters1 = {
        l: string1.lower().count(l) for l in set(string1.lower()) if l.isalpha()
    }
    letters2 = {
        l: string2.lower().count(l) for l in set(string2.lower()) if l.isalpha()
    }

    return letters1 == letters2


is_anagram = is_anagram_v2