'Steals a reference to `item`.'

def tuple_setitem(self, tuple_val, index, item):

    fnty = Type.function(Type.int(), [self.pyobj, Type.int(), self.pyobj])
    setitem_fn = self._get_function(fnty, name='PyTuple_SetItem')
    index = self.context.get_constant(types.int32, index)
    self.builder.call(setitem_fn, [tuple_val, index, item])
