ROS2 Dashing: No seconds() in Time_ struct

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Hi,

While trying to compile the image message callback function in a ROS2 node below,

void imageCallback(const sensor_msgs::msg::Image::ConstSharedPtr& img_msg) {
      double cur_time = img_msg->header.stamp.seconds();
      ...
}

I get the following compilation error:

const struct builtin_interfaces::msg::Time_<std::allocator<void>> has no member named ‘seconds’

How do I solve this issue?