'Filter so that only time markers `<timeslot>...</timeslot>` of
the correct timeslot remains in the description.
Args:
raw_desc (str): The unmodified description.
curr_time (str): A timeslot identifier.
Returns:
description (str): A possibly moified description.'

def replace_timeslots(self, raw_desc, curr_time):

    if raw_desc:
        regextuple = REGEXMAP[curr_time]
        raw_desc = regextuple[0].sub('\\1', raw_desc)
        raw_desc = regextuple[1].sub('', raw_desc)
        raw_desc = regextuple[2].sub('', raw_desc)
        return regextuple[3].sub('', raw_desc)
    return raw_desc
