from typing import Iterable
from typing import Any


def is_in(header_value: Iterable, rule_value: Any) -> bool:
    """
    Checks whether *rule* exists within *value*.

    Parameters
    ----------
    value : Iterable
        An iterable of any kind
    rule : Any
        An object to look for in *value*

    Returns
    -------
    bool
        Whether *rule* exists in *value*
    """
    return rule_value in header_value if header_value else False