input: Write a python function to remove duplicate strings from a list.
  assert remove_duplicates(['abc', 'def', 'abc', 'ghi', 'ghi', 'ghi', 'xyz'])==['abc', 'def', 'ghi', 'xyz']
  assert remove_duplicates(['apple', 'banana', 'apple', 'apple', 'cherry'])==['apple', 'banana', 'cherry']
  assert remove_duplicates(['one', 'two', 'three', 'two', 'one'])==['one', 'two', 'three']
output: def remove_duplicates(strings):
      seen = set()
      result = []
      for string in strings:
          if string not in seen:
              seen.add(string)
              result.append(string)
      return result