Code is able to upload but not working with arduino uno

Hello, I wanted to turn on and off LED connected on digital pin 13 using Pyfirmata from Anaconda, spyder. The problem is no matter which digital pin I give, it is only affecting the RX LED. I have tried same connection with same logic code in arduino IDE to make sure the connection is right. It is working fine with arduino IDE not with python. There are also no error messages coming. I am using anaconda spyder 2.7, 64 bit on 64 bit windows 10. I am writing you the code also. Can anyone try this code and suggest me where I am doing wrong. Thanks.

code: from pyfirmata import Arduino , util import time board = Arduino ('COM3') iterator = util.Iterator(board) iterator.start () LED_blink = board.get_pin('d:13:o') // Only RX pin is blinking, tried other pin but same result LED_blink.write(1) time.sleep(0.1) LED_blink.write(0) time.sleep(0.1) board.exit()

If you have no problem with the Arduino IDE but you do with "Pyfirmata", why are you here if it's clearly a problem with Pyfirmata ...