.. efun:: mixed restore_value(string str)

  Decode the string representation :arg:`str` of a value back into the value itself and return it. :arg:`str` is a string as generated by :efun:`save_value`.

  The ``#x:y`` version specification of the saveformat is optional, however the driver will assume the old format version 0 in this case. It is strongly recommended to regard the version specification as non-optional in newly saved values.

  .. todo:: ditto re: saveformat documentation

  :history 3.2.8 introduced:
  :history 3.2.9 changed: added restoring of non-lambda closures, symbols, and quoted arrays, using a new savefile format version 1.
  :history 3.5.0 changed: added the possibility to restore version 2 with its higher float precision.

  .. seealso:: :efun:`save_value`, :efun:`restore_object`, :efun:`save_object`