sage: save(FreeGroup(1)/[], 'ab')
sage: load('ab.sobj')
Finitely presented group < x |  >
sage: from sage.groups.finitely_presented import wrap_FpGroup
sage: save(wrap_FpGroup(libgap(FreeGroup(1)/[])), 'ab')
sage: load('ab.sobj')
---------------------------------------------------------------------------
GAPError                                  Traceback (most recent call last)
Cell In[20], line 1
----> 1 load('ab.sobj')

File /usr/local/sage-310/src/sage/misc/persist.pyx:189, in sage.misc.persist.load()
    187 
    188     ## Load file by absolute filename
--> 189     with open(filename, 'rb') as fobj:
    190         X = loads(fobj.read(), compress=compress, **kwargs)
    191     try:

File /usr/local/sage-310/src/sage/misc/persist.pyx:190, in sage.misc.persist.load()
    188 ## Load file by absolute filename
    189 with open(filename, 'rb') as fobj:
--> 190     X = loads(fobj.read(), compress=compress, **kwargs)
    191 try:
    192     X._default_filename = os.path.abspath(filename)

File /usr/local/sage-310/src/sage/misc/persist.pyx:995, in sage.misc.persist.loads()
    993 unpickler = SageUnpickler(io.BytesIO(s), **kwargs)
    994 global already_unpickled
--> 995 ans = unpickler.load()
    996 already_unpickled = { }
    997 return ans

File /usr/local/sage-310/src/sage/libs/gap/element.pyx:390, in sage.libs.gap.element._from_sage()
    388 
    389 
--> 390 cpdef _from_sage(elem) noexcept:
    391     """
    392     Currently just used for unpickling; equivalent to calling ``libgap(elem)``

File /usr/local/sage-310/src/sage/libs/gap/element.pyx:396, in sage.libs.gap.element._from_sage()
    394 """
    395 if isinstance(elem, str):
--> 396     return libgap.eval(elem)
    397 
    398 return libgap(elem)

File /usr/local/sage-310/src/sage/libs/gap/libgap.pyx:406, in sage.libs.gap.libgap.Gap.eval()
    404 
    405         initialize()
--> 406         elem = make_any_gap_element(self, gap_eval(gap_command))
    407 
    408         # If the element is NULL just return None instead

File /usr/local/sage-310/src/sage/libs/gap/util.pyx:364, in sage.libs.gap.util.gap_eval()
    362 try:
    363     GAP_Enter()
--> 364     result = GAP_EvalString(cmd)
    365     # We can assume that the result object is a GAP PList (plain list)
    366     # and we should use functions for PLists directly for now; see

GAPError: Error, Variable: 'x' must have a value