It is giving error while working with keys having : in it

I am going to send XML response from my node js api.

When I am sending data like following

```
res.set('Content-Type', 'text/xml');

let example5 = [
{
toys: [
{
_attr: {
decade: '80s',
locale: 'US'
}
},
{
toy: 'Transformers'
},
{
toy: [
{
_attr: {
knowing: 'half the battle'
}
},
'GI Joe'
]
},
{
toy: [
{
name: 'He-man'
},
{
'g:brand': 'He-man'
},
{
description: {
_cdata: 'Master of the Universe!'
}
}
]
}
]
}
]

return res.send(xml(example5, true));
```

When using the key with : it is giving error like this