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 also include methods to convert the item information to a string and to convert the item to a dictionary format.
  assert StoreItem(1, 'Laptop', 1200, 'High-performance laptop').__str__() == 'Laptop, $1200'
  assert StoreItem(2, 'Mouse', 20, 'Ergonomic mouse').__str__() == 'Mouse, $20'
  assert StoreItem(1, 'Laptop', 1200, 'High-performance laptop').to_dict() == {'item_id': 1, 'name': 'Laptop', 'price': 1200, 'description': 'High-performance laptop'}
  assert StoreItem(2, 'Mouse', 20, 'Ergonomic mouse').to_dict() == {'item_id': 2, 'name': 'Mouse', 'price': 20, 'description': 'Ergonomic mouse'}
  assert StoreItem(3, 'Keyboard', 50, 'Mechanical keyboard').__str__() == 'Keyboard, $50'
  assert StoreItem(3, 'Keyboard', 50, 'Mechanical keyboard').to_dict() == {'item_id': 3, 'name': 'Keyboard', 'price': 50, 'description': 'Mechanical keyboard'}
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
          }