Keep getting that Rate is not defined

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I am having some strange problem. When I run the python program I get an error that Rate is not defined:

line 30, in EncoderNodeLeft
    rate.sleep()
NameError: name 'rate' is not defined

Here is my code:

import time
#import ASUS.GPIO as GPIO
import rospy
from geometry_msgs.msg import PoseStamped
from nav_msgs.msg import Path
from std_msgs.msg import Int16


class EncoderNodeLeft:

    def __init__(self,encoder):
        self.tick = 0
        self.encoder = encoder
        self.pub = rospy.Publisher("lwheel", Int16, queue_size=1000)

    def tick_callback(self,channel):
        self.tick += 1
        if self.tick > 32766:
            self.tick = 0
        self.pub.publish(self.tick)

    def run(self):
        #GPIO.add_event_detect(self.encoder, GPIO.RISING, callback=self.tick_callback)
        rate = rospy.Rate(10) # 10hz
        while not rospy.is_shutdown():

            rate.sleep()

if __name__ == "__main__":
    try:
        rospy.init_node("encoder_node_left")
        encoder = 224
        encoder_node_left = EncoderNodeLeft(encoder)
        encoder_node_left.run()
    except rospy.ROSInterruptException:
        rospy.loginfo("There was an exception in encoder_node_left")