private boolean validTarget(TensorType target) {
        if (target.rank() == 1) // indexed or mapped 1d tensor
            return true;
        if (target.rank() == 2 && target.indexedSubtype().rank() == 1)
            return true; // mixed 2d tensor
        if(target.rank() == 2 && target.mappedSubtype().rank() == 2)
            return true; // mapped 2d tensor
        if (target.rank() == 3 && target.indexedSubtype().rank() == 1)
            return true; // mixed 3d tensor
        return false;
    }
@return the requested embedder id. This will diverge from the selected embedder's id when executed in config-model
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/EmbedExpression.java