public static TensorType createTensorType(String featureName, ExpressionNode argument) {
        try {
            int length = Integer.parseInt(argument.toString());
            return new TensorType.Builder(TensorType.Value.FLOAT).indexed("d0", 1).indexed("d1", length).build();
        } catch (NumberFormatException ex) {
            throw new IllegalArgumentException("Invalid argument to " + featureName + ": the first argument must be " +
                    "the length to the token sequence to generate. Got " + argument);
        }
    }
Transforms a feature of the form

    tokenAttentionMask(128, a, b, ...)

to an expression that generates a tensor that has values 1 for all
arguments (including CLS and SEP tokens) and 0 for the rest of the
sequence.

Concretely, transforms to a tensor generation expression:

    tensor(d0[1],d1[128])(if(d1 < 1 + length_a + 1 + length_b + 1 + ..., 1, 0))
config-model/src/main/java/com/yahoo/schema/expressiontransforms/TokenTransformer.java