input: Write a function to remove duplicate entries from a list. The function should return a new list with all unique elements in the order they first appeared. If the input list is empty, the function should return an empty list.
  assert removeDuplicates([1,2,2,3,3,4])==[1,2,3,4]
  assert removeDuplicates([1,1,1,1,1])==[1]
  assert removeDuplicates([2,4,6,8,6,4,2])==[2,4,6,8]
  assert removeDuplicates([])==[]
output: def removeDuplicates(lst):
      seen = set()
      result = []
      for item in lst:
          if item not in seen:
              seen.add(item)
              result.append(item)
      return result