input: Write a function to create a Python class for an online store item that includes fields for ID, name, price, and description. The class should have an initializer method (__init__) to set these attributes and a __str__ method to return a string representation of the item. Additionally, include a method named to_dict that returns a dictionary representation of the item's attributes.
  assert StoreItem(1, "Laptop", 999, "A high-performance laptop")
  assert str(StoreItem(1, "Laptop", 999, "A high-performance laptop")) == "Laptop, $999"
  assert StoreItem(1, "Laptop", 999, "A high-performance laptop").to_dict() == {'item_id': 1, 'name': 'Laptop', 'price': 999, 'description': 'A high-performance laptop'}
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
          }