(
  source only properties:
  {
    "driver": "file",
    "filename": "/var/lib/libvirt/images/a"
  }
  backing store string:
  /var/lib/libvirt/images/a
)
(
  source only properties:
  {
    "driver": "file",
    "filename": "/var/lib/libvirt/images/b"
  }
  backing store string:
  /var/lib/libvirt/images/b
)
(
  source only properties:
  {
    "driver": "nbd",
    "server": {
      "type": "inet",
      "host": "test.org",
      "port": "10809"
    },
    "export": "images/c"
  }
  backing store string:
  nbd://test.org:10809/images/c
)
(
  source only properties:
  {
    "driver": "file",
    "filename": "/var/lib/libvirt/images/d"
  }
  backing store string:
  /var/lib/libvirt/images/d
)