input: Write a python function to filter out strings from a list without duplicates.
  assert filter_out_strings(['apple', 'zoo', 'banana', 'foo', 'apple', 'banana']) == ['apple', 'zoo', 'banana', 'foo']
  assert filter_out_strings(['dog', 'cat', 'dog', 'fish', 'bird']) == ['dog', 'cat', 'fish', 'bird']
  assert filter_out_strings(['hello', 'world', 'hello', 'python', 'world']) == ['hello', 'world', 'python']
output: def filter_out_strings(lst):
      seen = set()
      result = []
      for item in lst:
          if item not in seen:
              seen.add(item)
              result.append(item)
      return result