human
Complete the below
def make_events(add_nulls):

    ''''Every event has at least three pieces of data associated with it:
    1. sid : The ID of the asset associated with the event.
    2. event_date : The date on which an event occurred.
    3. timestamp : The date on which we learned about the event.
    This can be before the occurence_date in the case of an
    announcement about an upcoming event.
    Events for two different sids shouldn\'t interact in any way, so the
    interesting cases are determined by the possible interleavings of
    event_date and timestamp for a single sid.
    Fix two events with dates e1, e2 and timestamps t1 and t2.
    Without loss of generality, assume that e1 < e2. (If two events have the
    same occurrence date, the behavior of next/previous event is undefined).
    The remaining possible sequences of events are given by taking all possible
    4-tuples of four ascending dates. For each possible interleaving, we
    generate a set of fake events with those dates and assign them to a new
    sid.'
    '''
assistant
#Here is Python program to fix two events with dates e1, e2 and timestamps t1 and t2.
    def gen_date_interleavings():
        for (e1, e2, t1, t2) in product(*([critical_dates] * 4)):
            if (e1 < e2):
                (yield (e1, e2, t1, t2))
    event_frames = []
    for (sid, (e1, e2, t1, t2)) in enumerate(gen_date_interleavings()):
        event_frames.append(make_events_for_sid(sid, [e1, e2], [t1, t2]))
    if add_nulls:
        for date in critical_dates:
            event_frames.append(make_null_event_date_events(np.arange((sid + 1)), timestamp=date))
    return pd.concat(event_frames, ignore_index=True)