def singleton(cls):
    """
    Decorator for making a class a singleton.
    This ensures that only one instance of the class exists.
    """
    instances = {}  # Dictionary to store the instance of the singleton class

    def get_instance(*args, **kwargs):
        """
        If an instance of the class does not exist, create one and store it.
        If it exists, return the existing instance.
        """
        if cls not in instances:
            instances[cls] = cls(*args, **kwargs)
        return instances[cls]

    return get_instance