+ """Returns a string composed of the parent process' id, the current
+ process' id and the current thread identifier. The former two are
+ numbers (pids) whereas the latter is a thread id passed during thread
+ creation time.
+
+ >>> ret = current_thread_id()
+ >>> (ppid, pid, tid) = ret.split('/')
+ >>> ppid.isnumeric()
+ True
+ >>> pid.isnumeric()
+ True
+
+ """