Question: how do I use the omap tag?

For example,

```
yaml = require`tinyyaml`
doc = [[
t: !!omap
  a: 1
  b: 2
  c: 3
  d: 4
]]

t = yaml.parse(doc).t

for k, v in pairs(t) do
    print(k, v)
end
```

does not guarantee order. Is there a different iteration function I can use?