input: Write a python function to order items by their popularity.
  assert order_items_by_popularity(['apple', 'banana', 'apple', 'orange', 'banana', 'apple']) == ['apple', 'banana', 'orange']
  assert order_items_by_popularity(['cat', 'dog', 'cat', 'bird', 'dog', 'dog']) == ['dog', 'cat', 'bird']
  assert order_items_by_popularity(['pen', 'pencil', 'pen', 'pen', 'marker']) == ['pen', 'pencil', 'marker']
output: def order_items_by_popularity(items):
      from collections import Counter
      count = Counter(items)
      sorted_items = sorted(count.keys(), key=lambda x: (-count[x], x))
      return sorted_items