input: Write a function to find the most common fruit name from a list. If there are multiple fruits with the same highest frequency, return the first one encountered in the list. If the list is empty, return None. The function should be named most_common_fruit and should take a single parameter, fruit_list.
  assert most_common_fruit(['Apple', 'Orange', 'Apple', 'Pineapple', 'Grape', 'Apple'])=='Apple'
  assert most_common_fruit(['Orange', 'Apple', 'Pineapple', 'Grape', 'Apple', 'Orange'])=='Orange'
  assert most_common_fruit([])==None
  assert most_common_fruit(['Pineapple', 'Grape', 'Pineapple', 'Grape', 'Grape'])=='Grape'
output: def most_common_fruit(fruit_list):
      if not fruit_list:
          return None
      fruit_count = {}
      for fruit in fruit_list:
          if fruit in fruit_count:
              fruit_count[fruit] += 1
          else:
              fruit_count[fruit] = 1
      most_common = max(fruit_count, key=fruit_count.get)
      return most_common