I think the docs cover this well enough, but I think it would be easier to parse the actual code by aligning to the margin instead of preceding braces:

```python
_quads = {
    "host": {
      	"no_vm": ("a", 'txt'),
       	"state": ("b", 'img'),
       	"vendor": ("c", 'img'),
       	"creds": ("d", 'img')
    },
    "infra_prov": {
    	"no_host": ("a", 'txt'),
       	"vendor": ("c", 'img'),
       	"creds": ("d", 'img'),
    },
    "vm": {
    	"os": ("a", 'img'),
       	"state": ("b", 'img'),
       	"vendor": ("c", 'img'),
       	"no_snapshot": ("d", 'txt'),
       	"policy": ("g", 'img'),
    },
    "cloud_prov": {
    	"no_vm": ("a", 'txt'),
       	"no_image": ("b", 'txt'),
       	"vendor": ("b", 'img'),
       	"creds": ("d", 'img'),
    },
    "instance": {
    	"os": ("a", 'img'),
       	"state": ("b", 'img'),
       	"vendor": ("c", 'img'),
       	"no_snapshot": ("d", 'txt'),
       	"policy": ("g", 'img'),
    },
}
```

This way is (I think) much easier to scan for quad types and the attributes available for each type.