input: Write a function to classify items as 'fruit' or 'vegetable'.
  assert classify(['apple', 'carrot', 'tomato', 'cherry']) == ['fruit', 'vegetable', 'vegetable', 'fruit']
  assert classify(['banana', 'lettuce', 'grape']) == ['vegetable', 'vegetable', 'fruit']
  assert classify(['strawberry', 'potato', 'peach']) == ['fruit', 'vegetable', 'fruit']
output: def classify(items):
      fruits = {'apple', 'banana', 'cherry', 'grape', 'peach', 'strawberry'}
      vegetables = {'carrot', 'tomato', 'lettuce', 'potato'}
      result = []
      for item in items:
          if item in fruits:
              result.append('fruit')
          elif item in vegetables:
              result.append('vegetable')
      return result