input: Write a function to find the mode of a given set of values. The mode is the value that appears most frequently in the set. If multiple values have the same highest frequency, you can return any one of them. If the input list is empty, return None.
  
  def find_mode(list):
    if not list:
      return None
    max_count = 0
    mode = list[0]
    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, 2, 3, 4, 5])==1
  assert find_mode([1, 1, 2, 3, 4, 4])==1
  assert find_mode([])==None
output: def find_mode(list):
    if not list:
      return None
    max_count = 0
    mode = list[0]
    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