docs: def _inspect_disk(self):
          """Inspects the disk and returns the mountpoints mapping
          as a list which order is the supposed one for correct mounting.
  
          """
          roots = self._handler.inspect_os()
  
          if roots:
              self._root = roots[0]
              return sorted(self._handler.inspect_get_mountpoints(self._root),
                            key=lambda m: len(m[0]))
          else:
              raise RuntimeError("No OS found on the given disk image.")