Enhance the einsum converter

[LongerZrLong]

Hi there, I notice that the einsum converter can only handle the case: torch.einsum(eq, x, y) while not the case: torch.einsum(eq, [x, y]).

[jaybdub]

Hi @LongerZrLong ,

Thanks for the PR! Looks good to me.

Will test and likely merge soon.

Best, John