private Tensor embedSingleValue(ExecutionContext context) {
        StringFieldValue input = (StringFieldValue)context.getCurrentValue();
        return embed(input.getString(), getOutputTensorType(), context);
    }
@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