input: Write a python function to remove duplicates from a list.
  assert removeDuplicates([1, 2, 3, 2, 5, 4, 3, 1]) == [1, 2, 3, 5, 4]
  assert removeDuplicates([10, 20, 20, 30, 40, 40, 50]) == [10, 20, 30, 40, 50]
  assert removeDuplicates([7, 7, 7, 7, 7, 7]) == [7]
output: def removeDuplicates(lst):
      seen = set()
      unique_lst = []
      for item in lst:
          if item not in seen:
              unique_lst.append(item)
              seen.add(item)
      return unique_lst