Solved by ptrblck in post #2 
              
              
                I don’t think it’s possible to add this “symbolic” None dimension to a PyTorch tensor (at least not in the standard eager tensors), as it wouldn’t be needed. If I’m not mistaken, Keras (and/or TF) uses it to specify a dimension with a variable size. If so, you can just use a different (batch) size i…