@Override
    public String toString(ToStringContext<NAMETYPE> context) { return type + "(" + generatorToString(context) + ")"; }
Creates a generated tensor from a bound function

@param type the type of the tensor
@param generator the function generating values from a list of numbers specifying the indexes of the
                 tensor cell which will receive the value
@throws IllegalArgumentException if any of the tensor dimensions are not indexed bound
vespajlib/src/main/java/com/yahoo/tensor/functions/Generate.java