input: Write a python function to remove duplicate strings from a list.
  assert remove_duplicates(["apple", "banana", "apple", "orange", "banana"]) == ["apple", "banana", "orange"]
  assert remove_duplicates(["cat", "dog", "cat", "dog", "elephant"]) == ["cat", "dog", "elephant"]
  assert remove_duplicates(["x", "y", "z", "x", "y", "z"]) == ["x", "y", "z"]
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