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. If the list is empty, return None.
  def find_mode(list):
    if len(list) == 0:
      return None
    max_count = 0
    mode = None
    count = {}
    for item in list:
      if item in count:
        count[item] += 1
      else:
        count[item] = 1
      if count[item] > max_count:
        max_count = count[item]
        mode = item
    return mode
  assert find_mode([1, 2, 3, 2, 4, 2])==2
  assert find_mode([1, 1, 2, 2, 3, 3]) in [1, 2, 3]
  assert find_mode([4, 5, 6, 7, 8])==4
  assert find_mode([])==None
  assert find_mode([10, 10, 10, 20, 20, 20, 30, 30]) in [10, 20]
output: def find_mode(list):
    if len(list) == 0:
      return None
    max_count = 0
    mode = None
    count = {}
    for item in list:
      if item in count:
        count[item] += 1
      else:
        count[item] = 1
      if count[item] > max_count:
        max_count = count[item]
        mode = item
    return mode