Logged In: YES 
user_id=4771

Subscripting is generally a bit sloppy: e.g. the AST model has
no way to distinguish between a single value and a one-element
tuple value!  See:

>>> d = {}
>>> d[1,] = 6
>>> d
{1: 6}        # !

I suggest we fix the model to turn the 'subs' of the 'Subscript' node
from a list of nodes to a single, mandatory 'sub' node.  If tupling is
necessary, it can be explicitly represented with a 'sub' containing a
'Tuple' node.