from typing import Any


def modifier(key: str, value: Any) -> tuple[str, dict[str, Any]]:
    """Key to modifier value.

    Args:
        key (str): Any str with `__` and modifier.
        value (Any): Any value.

    Returns:
        tuple[str, dict[str, Any]]: Key and dictionary value.
    """
    key, suffix = key.split("__")
    return (key, {"$%s" % suffix: value})