Goal
Given a list of elements [a1, a2, ..., an], with each ai being a string, write a function **majority** that returns the value that appears the most in the list. 
If there's no winner, the function should return None, NULL, nil, etc, based on the programming language.
Example
majority(["A", "B", "A"]) returns "A"
majority(["A", "B", "B", "A"]) returns None
from collections import Counter

def majority(arr):
    c = Counter(arr)
    t = c.most_common(2)
    if len(t) == 1 or len(t) > 1 and t[1][1] < t[0][1]:
        return t[0][0]
    return None
from collections import Counter

def majority(arr):
    c = Counter(arr)
    t = c.most_common(2)
    if len(t) == 1 or len(t) > 1 and t[1][1] < t[0][1]:
        return t[0][0]
    return None