input: Write a function to return the most common fruit name from a list of fruit names. If there is a tie for the most common fruit, return the first one encountered. If the list is empty, return None.
  
  def most_common_fruit(fruit_list):
      if not fruit_list:
          return None
      
      freq_dict = {}
      for fruit in fruit_list:
          if fruit in freq_dict:
              freq_dict[fruit] += 1
          else:
              freq_dict[fruit] = 1
      
      max_freq = max(freq_dict.values())
      for fruit in fruit_list:
          if freq_dict[fruit] == max_freq:
              return fruit
  
  assert most_common_fruit(['Apple', 'Orange', 'Apple', 'Pineapple', 'Grape', 'Apple']) == 'Apple'
  assert most_common_fruit(['Orange', 'Grape', 'Grape', 'Orange', 'Peach']) == 'Orange'
  assert most_common_fruit([]) == None
  assert most_common_fruit(['Cherry', 'Pomegranate', 'Cherry']) == 'Cherry'
  assert most_common_fruit(['Kiwi', 'Kiwi', 'Kiwi', 'Pineapple', 'Pineapple']) == 'Kiwi'
output: def most_common_fruit(fruit_list):
      if not fruit_list:
          return None
      
      freq_dict = {}
      for fruit in fruit_list:
          if fruit in freq_dict:
              freq_dict[fruit] += 1
          else:
              freq_dict[fruit] = 1
      
      max_freq = max(freq_dict.values())
      for fruit in fruit_list:
          if freq_dict[fruit] == max_freq:
              return fruit