input: Write a function to generate a Python class for an online store item that includes fields for ID, name, price, and description. The class should have an initializer method to set these fields, a string representation method to return the item's name and price formatted as 'name, $price', and a method to convert the item object 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', 999.99, 'High-performance laptop')) == 'Laptop, $999.99'
  assert StoreItem(2, 'Mouse', 19.99, 'Wireless mouse').to_dict() == {
      'item_id': 2,
      'name': 'Mouse',
      'price': 19.99,
      'description': 'Wireless mouse'
  }
  assert StoreItem(3, 'Keyboard', 49.99, 'Mechanical keyboard').name == 'Keyboard'
  assert StoreItem(4, 'Monitor', 199.99, '24-inch monitor').price == 199.99
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
          }
  