text: def mode(arr):
      if not arr:
          return set()
      counts = {}
      for num in arr:
          if num not in counts:
              counts[num] = 1
          else:
              counts[num] += 1
      maximum = max(counts.values())
      return {num for num in arr if counts[num] == maximum}
  
  
  print(mode([])) # {}
  print(mode([1,2,3,3,4])) # {3} 
  print(mode([1,2,3,4,3,4])) # {3,4}