old_contents: import bisect
  import collections
  
  PriceEvent = collections.namedtuple("PriceEvent", ["timestamp", "price"])
  
  
  class Stock:
      def __init__(self, symbol):
          self.symbol = symbol
          self.price_history = []
  
      @property
      def price(self):
          return self.price_history[-1].price if self.price_history else None
  
      def update(self, timestamp, price):
          if price < 0:
              raise ValueError("price should not be negative")
          bisect.insort_left(self.price_history, PriceEvent(timestamp, price))
  
      def is_increasing_trend(self):
          return self.price_history[-3].price < self.price_history[-2].price < self.price_history[-1].price
  
new_contents: import bisect
  import collections
  
  PriceEvent = collections.namedtuple("PriceEvent", ["timestamp", "price"])
  
  
  class Stock:
      def __init__(self, symbol):
          """Constructor for Stock instance.
  
          Args:
              symbol: The stock symbol.
          """
          self.symbol = symbol
          self.price_history = []
  
      @property
      def price(self):
          """Returns the stocks most recent price.
  
          Returns: Most recent price.
  
          """
          return self.price_history[-1].price if self.price_history else None
  
      def update(self, timestamp, price):
          """Updates the stock's price history.
  
          Args:
              timestamp: The timestamp of the update.
              price: The new price of the stock.
          """
          if price < 0:
              raise ValueError("price should not be negative")
          bisect.insort_left(self.price_history, PriceEvent(timestamp, price))
  
      def is_increasing_trend(self):
          """Determines if last three prices were ascending in value.
  
          Returns: True if there is an increasing trend, False if not.
  
          """
          return self.price_history[-3].price < self.price_history[-2].price < self.price_history[-1].price
  
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