input: Write a function to find the mode of a list of numbers.
  assert mode([1, 2, 5, 2, 3, 2, 5, 2]) == 2
  assert mode([4, 4, 1, 2, 4, 3, 2, 4, 1]) == 4
  assert mode([1, 1, 2, 3, 3, 3, 2, 1, 1]) == 1
output: def mode(numbers):
      from collections import Counter
      count = Counter(numbers)
      return count.most_common(1)[0][0]