def filter_object(exp, filter):
    """Filters an event log using categorical columns, can be used on exploded event logs to filter object, since they become categorical through the explosion.
    Note that this filters in CNF, i.e. a logical and on `filter` and logical or on the list contained in each item

    Args:
        exp (pd.DataFrame): (exploded) event log
        filter (dict): a dictionary containing (str,list) pairs where str is a df-column name and list is a list of values

    Returns:
        exp: A filtered dataframe
    """
    for object, values in filter.items():
        exp = exp[exp[object].isin(values)]
    return exp