i am trying to connect to the "/oak/points" topic i am not receiving any data following is my code:

Copyright 2016 Open Source Robotics Foundation, Inc.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

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# See the License for the specific language governing permissions and

# limitations under the License.

import rclpy

from rclpy.node import Node

from rclpy.qos import QoSProfile, ReliabilityPolicy

# from std_msgs.msg import CameraInfo

from sensor_msgs.msg import CameraInfo, Image, PointCloud2

class MinimalSubscriber(Node):

def __init__(self):

    super().__init__('minimal_subscriber')

   # qos_profile = QoSProfile(reliability=ReliabilityPolicy.BEST_EFFORT, depth=10)

    qos_policy = rclpy.qos.QoSProfile(reliability=rclpy.qos.ReliabilityPolicy.BEST_EFFORT,

                                      history=rclpy.qos.HistoryPolicy.KEEP_LAST,

                                      depth=1)

    self.subscription = self.create_subscription(

        PointCloud2,

        '/oak/points',

        self.listener_callback,

         qos_profile=qos_policy)

    self.subscription  # prevent unused variable warning

def listener_callback(self, msg):

    self.get_logger().info('I heard: "%s"' % msg)

def main(args=None):

rclpy.init(args=args)

minimal_subscriber = MinimalSubscriber()

rclpy.spin(minimal_subscriber)

# Destroy the node explicitly

# (optional - otherwise it will be done automatically

# when the garbage collector destroys the node object)

minimal_subscriber.destroy_node()

rclpy.shutdown()

if name == 'main':

main()