input: Write a function to create a Python class for an online store item that includes fields for ID, name, price, and description. Include methods to return a string representation of the item and to convert the item to a dictionary. The function should return the class definition. Additionally, provide assert statements to verify the class methods.
  
  class create_store_item_class():
      def __init__(self):
          self.class_definition = """
  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
          }
  """
          return self.class_definition
  
  assert create_store_item_class().class_definition.strip() == """
  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
          }
  """.strip()
  
  item = StoreItem(1, 'Laptop', 999.99, 'A high-performance laptop.')
  assert str(item) == 'Laptop, $999.99'
  assert item.to_dict() == {'item_id': 1, 'name': 'Laptop', 'price': 999.99, '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
          }