Problem: Valid Anagram

Given two strings, str1 and str2, check whether str2 is an anagram of str1.

An anagram is a word or phrase created by rearranging the letters of another word or phrase while utilizing each of the original letters exactly once.

Constraints:

• $1 \leq$ str1.length, str2.length $\leq 10^3$

• str1 and str2 consist of only lowercase English letters.