Valid Anagram

Return whether a and b contain exactly the same characters with the same multiplicities. Order does not matter; case, spaces, and Unicode characters do matter. Do not normalize the text. Empty strings are anagrams of each other. Each string has at most 1000 characters. Examples (JSON; null means Python None): Input: {"a": "anagram", "b": "nagaram"} Output: true Input: {"a": "rat", "b": "car"} Output: false

def valid_anagram(a: str, b: str) -> bool:
    """Compare exact character multiplicities."""
    pass