
    Given a list of bus routes and their current passenger counts, find the route number that currently has the lowest passenger occupancy. Each route is represented as a pair containing the route number and its current passenger count.
    

    
from operator import itemgetter

def index_minimum(test_list):
    """
    Given a list of bus routes and their current passenger counts, find the route number that currently has the lowest passenger occupancy. Each route is represented as a pair containing the route number and its current passenger count.
    

    """
from operator import itemgetter

def index_minimum(test_list):
    """
    Given a list of bus routes and their current passenger counts, find the route number that currently has the lowest passenger occupancy. Each route is represented as a pair containing the route number and its current passenger count.
    

    """
    res = min(test_list, key=itemgetter(1))[0]
    return res