input: Write a function that defines a Python class for an online store item, including fields for ID, name, price, and description. The class should also have methods to convert the item to a string and to a dictionary.
  
  class StoreItem:
      def __init__(self, item_id, name, price, description):
          self.item_id = item_id
          self.name = name
          self.price = price
          self.description = description
  
      def __str__(self):
          return f'{self.name}, ${self.price}'
  
      def to_dict(self):
          return {
              'item_id': self.item_id,
              'name': self.name,
              'price': self.price,
              'description': self.description
          }
  
  assert str(StoreItem(1, "Laptop", 1200, "High-performance laptop"))=="Laptop, $1200"
  assert StoreItem(2, "Mouse", 25, "Wireless mouse").to_dict()=={'item_id': 2, 'name': 'Mouse', 'price': 25, 'description': 'Wireless mouse'}
  assert StoreItem(3, "Keyboard", 50, "Mechanical keyboard").to_dict()=={'item_id': 3, 'name': 'Keyboard', 'price': 50, 'description': 'Mechanical keyboard'}
  assert str(StoreItem(4, "Monitor", 300, "27-inch monitor"))=="Monitor, $300"
  assert StoreItem(5, "Headphones", 150, "Noise-cancelling headphones").to_dict()=={'item_id': 5, 'name': 'Headphones', 'price': 150, 'description': 'Noise-cancelling headphones'}
output: class StoreItem:
      def __init__(self, item_id, name, price, description):
          self.item_id = item_id
          self.name = name
          self.price = price
          self.description = description
  
      def __str__(self):
          return f'{self.name}, ${self.price}'
  
      def to_dict(self):
          return {
              'item_id': self.item_id,
              'name': self.name,
              'price': self.price,
              'description': self.description
          }