selector behavior difference , Combinations or Arrangements list

edit

HI

I opened this question first then I deleted it after a while now I re-open it because finally I do not know if its a pb or not!. sorry for my versatile behavior

Ubuntu 18.04 , SageMath 9.0 notebook

why if I uncoment line 3 of the code below, I get TraitError: Invalid selection: value not found. but code is ok if line 3 commented

anIndexL=[1..5]
anCoupleIndexL=Arrangements(anIndexL,2).list()
#anCoupleIndexL=Combinations(anIndexL,2).list()
show(anCoupleIndexL)

@interact
def _( nbStepMax=slider(1,20,1,default=20),anCouple = selector(anCoupleIndexL,default=anCoupleIndexL[0])):
    show(anCouple)

Arrangements return object parent is 𝙰𝚛𝚛𝚊𝚗𝚐𝚎𝚖𝚎𝚗𝚝𝚜 𝚘𝚏 𝚝𝚑𝚎 𝚜𝚎𝚝[𝟷,𝟸,𝟹,𝟺,𝟻] 𝚘𝚏 𝚕𝚎𝚗𝚐𝚝𝚑 𝟸

As Combinations return object is a simple list.

anIndexL=[1..5]
anCoupleIndexL0=Arrangements(anIndexL,2).list()
anCoupleIndexL1=Combinations(anIndexL,2).list()
anCoupleIndexStrL0=[]
print("test parent couple for anCoupleIndexL0")

for an in anCoupleIndexL0 :
    anT=[]
    for e in an :
        show(e.parent())
    show(an.parent())
    anCoupleIndexStrL0.append(anT)

anCoupleIndexStrL1=[]
print("test parent couple for anCoupleIndexL1")
for an in anCoupleIndexL1 :
    anT=[]
    for e in an :
        show(e.parent())
    show(an.parent())
    anCoupleIndexStrL1.append(anT)