input: Write a python function to remove duplicates from a list.
  assert remove_duplicates([12, 34, 11, 12, 23, 11]) == [12, 34, 11, 23]
  assert remove_duplicates([1, 2, 2, 3, 4, 4, 5]) == [1, 2, 3, 4, 5]
  assert remove_duplicates([7, 7, 8, 9, 10, 10, 10]) == [7, 8, 9, 10]
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