'Constructor
@param event_id: a unique identifier for the event (e.g. record ID)
@param start: start time of the event (datetime.datetime)
@param end: end time of the event (datetime.datetime)
@param values: a dict of key-value pairs with the attribute
values for the event
@param row: the series row for this event
@param col: the series column for this event'

def __init__(self, event_id, start=None, end=None, values=None, row=DEFAULT, col=DEFAULT):

    self.event_id = event_id
    self.start = tp_tzsafe(start)
    self.end = tp_tzsafe(end)
    if isinstance(values, dict):
        self.values = values
    else:
        self.values = {}
    self.row = row
    self.col = col
    self._rows = None
    self._cols = None
