How do I implement a Gap function I wrote in a gap cell in cloudsage?

edit

I have written the following code in a cell:

%gap
OnChains:= function( c, g )
    local i, k;
    for i in [1..Length(c)] do
        k[i] := OnSetsSets(c[i], g);
    od;
  return k;
end;

But when I try and run

G.orbit(Set(K[0]), action = "OnChains")

in a sage cell, I get:

Error in lines 1-1
Traceback (most recent call last):
  File "/projects/b5d3c63b-a07d-41ae-905b-350044f6bb95/.sagemathcloud/sage_server.py", line 879, in execute
    exec compile(block+'\n', '', 'single') in namespace, locals
  File "", line 1, in <module>
  File "sage/misc/cachefunc.pyx", line 1896, in sage.misc.cachefunc.CachedMethodCaller.__call__ (build/cythonized/sage/misc/cachefunc.c:11488)
    w = self._cachedmethod._instance_call(self._instance, *args, **kwds)
  File "sage/misc/cachefunc.pyx", line 2552, in sage.misc.cachefunc.CachedMethod._instance_call (build/cythonized/sage/misc/cachefunc.c:14934)
    return self._cachedfunc.f(inst, *args, **kwds)
  File "/projects/sage/sage-6.7/local/lib/python2.7/site-packages/sage/groups/perm_gps/permgroup.py", line 1208, in orbit
    raise NotImplementedError("This action is not implemented (yet?).")
NotImplementedError: This action is not implemented (yet?).

Can someone help me implement my custom group action?