get_seat_type: (str) -> str The parameter represents a ticket. This function should return 'window', 'aisle', or 'middle' depending on the seat type. If the seat type is invalid, return the empty string. This function should make use of the provided constants in its return statements.

constants:

YEAR = 0
MONTH = 4
DAY = 6
FROM = 8
TO = 11
SEAT = 14
FLYER = 17

WINDOW = 'window'
AISLE = 'aisle'
MIDDLE = 'middle