ROS documentation "Used By"
On the documentation pages for ROS, found on http://www.ros.org/doc/api/index.html, each file's page has a section labeled "Used By: ". I assumed that this would be a list of files or packages that included this file, either directly or indirectly. However, some files that I know are included in others, such as XnCppWrapper.h, say that they are "Used By: None". What is this section actually supposed to mean?