chg: dev: use dict to determine dl type text.

[rachmadaniHaryono]

small improvement for dl type text. when new dl type added, the dl type text can be added on dict constant, directly below that.

also using type_ instead of _type to avoid python keyword (based on pep8)

single_trailingunderscore : used by convention to avoid conflicts with Python keyword, e.g.

https://www.python.org/dev/peps/pep-0008/

[rachmadaniHaryono]

there is also test branch here, but it require all module to have relative import rachmadaniHaryono/happypanda/dl-type-text-test