input: Write a function to find the mode of the given list of values. If the given list is empty then return None.
  def find_mode(list):
    if len(list) == 0:
      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([3, 3, 3, 4, 5, 6, 5])==3
  assert find_mode([1])==1
  assert find_mode([1, 2, 3, 4, 5])==1
  assert find_mode([]) is None
output: def find_mode(list):
    if len(list) == 0:
      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