input: 
  def predict(data):
      """ Predicts the class label for a given set of data using a pre-trained 
      decision tree classifier model.
      
      >>> predict([5.1, 3.5, 1.4, 0.2])
      ['Iris-setosa']
      >>> predict([6.2, 2.9, 4.3, 1.3])
      ['Iris-versicolor']
      """
      global model
      predicted_label = model.predict([data])
      return predicted_label
  
output:     global model
      predicted_label = model.predict([data])
      return predicted_label