input: Write a function to remove all duplicate elements from a given list while preserving the original order. The function should return the modified list.
  assert remove_duplicates([1, 3, 3, 5, 5, 7]) == [1, 3, 5, 7]
  assert remove_duplicates([2, 4, 4, 6, 8, 8, 10]) == [2, 4, 6, 8, 10]
  assert remove_duplicates([1, 1, 1, 1]) == [1]
  assert remove_duplicates([]) == []
  assert remove_duplicates([5, 7, 2, 5, 7, 2]) == [5, 7, 2]
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