This is perhaps a simple question, but I can't find the answer. How do I store key-value pairs where value is an array of numbers? For example:

```
 X = [1, [1,2,3]]
 Y = [4, [2,4,2]]

```

and so on. Which data structure should I use to store such one-to-many arrays?

EDIT:

I try to create a struct like this: struct(1, 1:3) but this gives an error "Field names must be strings." But I would need an integer here.