Returns the minimum input edge id that was snapped to this edge, or -1 if
no input edges were snapped (see SiblingPairs::CREATE). This is
useful for layers that wish to preserve the input edge ordering as much
as possible (e.g., to ensure idempotency).
Returns the minimum input edge id that was snapped to this edge, or -1 if no input edges were snapped (see SiblingPairs::CREATE). This is useful for layers that wish to preserve the input edge ordering as much as possible (e.g., to ensure idempotency).