I want to limit this on the 'simple' itags, and add -f 'dash' later. 
I created this map since information like dash or AHLS cannot be derived from extensions.

I was thinking of creating a big table contains all these itag related list/dict, not sure how you want to do it.

something like
```
_itag_map = { 
5: { ....},
13: {....},
```
and all current list/dict can be generated from it. easy for maintainance