input: Write a python function to delete duplicate elements in a list.
  assert deleteDuplicateElements([1, 2, 4, 2, 3, 4, 5]) == [1, 2, 4, 3, 5]
  assert deleteDuplicateElements([1, 1, 1, 1]) == [1]
  assert deleteDuplicateElements([5, 6, 5, 5, 6, 7]) == [5, 6, 7]
output: def deleteDuplicateElements(lst):
      seen = set()
      result = []
      for item in lst:
          if item not in seen:
              seen.add(item)
              result.append(item)
      return result