API Documentation: `SMODS.Rarity`

Required parameters:
- key
- loc_txt or localization entry (reference)
  - The only supported field is name. In localization files, it must be set as both misc.labels['k_'..key:lower()] and misc.dictionary['k_'..key:lower()].
Optional parameters (defaults):
- pools: Table with a list of ObjectType keys to add this rarity to. Skeleton:
```
{
    ["Joker"] = true, --uses self.default_rate when polled
    ["Joker"] = { rate = 0.7 },
}
```
- badge_colour: Colour of the rarity's badge.
- default_weight: Setting a numerical value for default_weight enables cards with this rarity to appear in the shop at the specified weight.
  - This sets a default weight, which can be modified by accessing G.GAME[key:lower() .. '_mod'] during a run.

API methods

get_weight(self, weight, object_type) -> number
- Returns weight. Use for finer control over the rarity's weight.
gradient(self, dt)
- Used to control the badge colour gradient.

SMODS.poll_rarity(_pool_key, _rand_key) -> key
- Polls all rarities tied to _pool_key and returns rarity key.