input: Write a python function to find the mode of a list of numbers.
  assert find_mode([1, 2, 3, 4, 4, 5, 6, 7, 8, 8, 8, 9]) == 8
  assert find_mode([10, 20, 20, 30, 30, 30, 40]) == 30
  assert find_mode([5, 5, 5, 5, 5]) == 5
output: def find_mode(numbers):
      from collections import Counter
      count = Counter(numbers)
      mode = max(count.keys(), key=lambda x: count[x])
      return mode