input: Write a function to remove duplicates from a given list and return the list in the same order. The function should use a method that preserves the original order of elements.
  
  assert remove_duplicates([1, 2, 3, 4, 3, 2, 1])==[1, 2, 3, 4]
  assert remove_duplicates([10, 22, 10, 20, 11, 22])==[10, 22, 20, 11]
  assert remove_duplicates([5, 5, 5, 5])==[5]
  assert remove_duplicates([])==[]
  assert remove_duplicates(["apple", "banana", "apple"])==["apple", "banana"]
output: def remove_duplicates(lst):
      seen = set()
      result = []
      for item in lst:
          if item not in seen:
              seen.add(item)
              result.append(item)
      return result