__all__ = ['assert_list', 'params_validators']

def assert_list(input_item):
    """
    Ensure the input is a list.

    If the input is not a list, it converts it into a single-element list.

    Parameters
    ----------
    input_item : any
        The item to be converted to a list if it is not already one.

    Returns
    -------
    list
        A list containing the input item(s). If input_item is None, returns an empty list.
    """
    if isinstance(input_item, list):
        return input_item
    elif input_item is not None:
        return [input_item]
    else:
        return []

def params_validators(key, value):
    """
    Validate and process a parameter for the NOAA studies.

    This function performs validations on parameter values such as latitude, longitude,
    keywords, and year ranges.

    Parameters
    ----------
    key : str
        The name of the parameter.
    value : any
        The value of the parameter.

    Returns
    -------
    None
        This function is currently a stub for validation logic.

    Notes
    -----
    Implement appropriate validations based on project requirements.
    """
    pass
