input: Write a function to delete all duplicates in a given list of numbers. Return the new list with all unique elements, maintaining the order of the first occurrences. If the input list is empty, return an empty list.
  assert deleteDuplicates([1, 2, 2, 3, 4, 4, 5])==[1, 2, 3, 4, 5]
  assert deleteDuplicates([5, 5, 5, 5, 5])==[5]
  assert deleteDuplicates([1, 2, 3, 4, 5])==[1, 2, 3, 4, 5]
  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