input: Write a function to delete all duplicates in a given list of numbers. The function should return a new list that contains only unique elements in the same order as they appear in the input list. If the input list is empty, the function should return an empty list.
  assert deleteDuplicates([1, 2, 3, 4, 1, 2])==[1, 2, 3, 4]
  assert deleteDuplicates([5, 5, 5, 5, 5])==[5]
  assert deleteDuplicates([10, 20, 30, 40])==[10, 20, 30, 40]
  assert deleteDuplicates([])==[]
output: def deleteDuplicates(nums):
      seen = set()
      result = []
      for num in nums:
          if num not in seen:
              seen.add(num)
              result.append(num)
      return result