+=head1 MULTIPLE HANDLES AND MULTIPLE THREADS
+
+All high-level libguestfs actions are synchronous. If you want
+to use libguestfs asynchronously then you must create a thread.
+
+Only use the handle from a single thread. Either use the handle
+exclusively from one thread, or provide your own mutex so that two
+threads cannot issue calls on the same handle at the same time.
+