input: Write a python function to remove duplicate elements from a list.
  assert remove_duplicates([10, 1, 2, 5, 1, 10, 3]) == [10, 1, 2, 5, 3]
  assert remove_duplicates([1, 2, 2, 3, 4, 4, 5]) == [1, 2, 3, 4, 5]
  assert remove_duplicates([5, 5, 5, 5, 5]) == [5]
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