private boolean validType(DataType type) {
        if ( ! (type instanceof TensorDataType tensorType)) return false;
        if ( tensorType.getTensorType().indexedSubtype().dimensions().size() != 1) return false;
        return true;
    }
Returns whether this is a valid input or output from this.
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/PackBitsExpression.java