code: def snap_to_beginning_of_week(day, weekday_start="Sunday"):
      
      delta_days = ((day.weekday() + 1) % 7) if weekday_start is "Sunday" else day.weekday()
      return day - timedelta(days=delta_days)
docs: Get the first day of the current week.
  
      :param day: The input date to snap.
      :param weekday_start: Either "Monday" or "Sunday", indicating the first day of the week.
      :returns: A date representing the first day of the current week.