input: Write a function to find the mode of the given set of values. The mode is the value that appears most frequently in the list. If there are multiple modes, return any one of them.
  assert find_mode([1, 2, 3, 2, 4, 2])==2
  assert find_mode([1, 1, 2, 2, 3, 3, 3, 4])==3
  assert find_mode([5])==5
  assert find_mode([5, 5, 5, 5])==5
  assert find_mode([])==None
output: def find_mode(values):
      if not values:
          return None
      count = {}
      for value in values:
          if value in count:
              count[value] += 1
          else:
              count[value] = 1
      mode = max(count, key=count.get)
      return mode