some dict's special methods

[nzcan]

hello,
i suppose that behind the:

>>> ca = {1:'koko', 2:'boko'}
>>> 1 in ca
True
>>> 5 in ca
False 

stays the dict's dunder '__contains__'
but i am not so sure which duner exactly stays behind:

>>> ca = {1:'koko', 2:'boko'}
>>> ca [3] = 'loko'
>>> ca 
{1: 'koko', 2: 'boko', 3: 'loko'}
>>> 

i think it could be '__setitem__', but i am not sure. is this '__setitem__' or some other special method? thanks in advance!