private static TensorType toTargetTensor(DataType dataType) {
        if (dataType instanceof ArrayDataType) return toTargetTensor(dataType.getNestedType());
        if  ( ! ( dataType instanceof TensorDataType))
            throw new IllegalArgumentException("Expected a tensor data type but got " + dataType);
        return ((TensorDataType)dataType).getTensorType();
    }
@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