analogWrite to PWM pins not working

# import the lib

from arduino import Arduino

import time
# specify the port as an argument

my_board = Arduino('COM5')
print my_board
# declare output pins as a list/tuple

my_board.output([9,10,11])
# perform operations

i=0
while(i<10):
print 'Writing Value'
val = my_board.analogWrite(11,255)
time.sleep(10)
i+=1

my_board.close()

This code hangs after 'Writing Value'
