Switch to use or not einsum op. Needed for ORT (#1456)
Co-authored-by: Gani Nazirov <ganaziro@microsoft.com>
Co-authored-by: Gani Nazirov <ganaziro@OrtTrainingDev4.af05slrtruoetgaxwwjv5nsq5e.px.internal.cloudapp.net>
Co-authored-by: Jeff Rasley <jerasley@microsoft.com>
