code: func (pfs *ProcFS) GetFullContainerName(pid int) (string, error) {
  	filePath := path.Join("/proc", strconv.Itoa(pid), "cgroup")
  	content, err := ioutil.ReadFile(filePath)
  	if err != nil {
  		if os.IsNotExist(err) {
  			return "", os.ErrNotExist
  		}
  		return "", err
  	}
  	return containerNameFromProcCgroup(string(content))
  }
docs: // getFullContainerName gets the container name given the root process id of the container.
  // E.g. if the devices cgroup for the container is stored in /sys/fs/cgroup/devices/docker/nginx,
  // return docker/nginx. Assumes that the process is part of exactly one cgroup hierarchy.