src/transformers/utils/fx.py/operator_getitem
def operator_getitem(a, b):
    def to_concrete(t):
        if isinstance(t, torch.Tensor):
            concrete = torch.ones_like(t, device="cpu")
            if concrete.dtype in [torch.float16, torch.float32, torch.float64, torch.int32]:
                concrete = concrete.to(torch.int64)
            return concrete
        return t

    if isinstance(a, torch.Tensor):
        # TODO: infer shape without performing the computation.
        if isinstance(b, tuple):
            b = tuple(map(to_concrete, b))
        else:
            b = to_concrete(b)
        return operator.getitem(torch.empty_like(a, device="cpu"), b).to("meta")
    return operator.getitem(a, b)