before index
my head_summary content is
end_pedestrian_collision,end_vehicle_collision,end_other_collision,weather,rep,start_point,initial_distance,final_distance,number_red_lights,exp_id,number_green_lights,final_time,result,end_point,time_out
after index
['end_pedestrian_collision', 'end_vehicle_collision', 'end_other_collision', 'weather', 'rep', 'start_point', 'initial_distance', 'final_distance', 'number_red_lights', 'exp_id', 'number_green_lights', 'final_time', 'result', 'end_point', 'time_ou']
in function get_causes_of_end
-2 seems to be -1