Config option not added

This adds (in theory) discovery to the maxcube component.
But this code does in fact not work at all. This might be because I’m daft, tired or perhaps because I’m sick right now, but I don’t get why the config option isn’t added. I always get:

2018-01-27 02:26:45 ERROR (MainThread) [homeassistant.config] Invalid config for [maxcube]: [discovery] is an invalid option for [maxcube]. Check: maxcube->maxcube->discovery. (See /home/thomas/.homeassistant/configuration.yaml, line 105). Please check the docs at eQ-3 MAX! - Home Assistant
2018-01-27 02:26:45 ERROR (MainThread) [homeassistant.setup] Setup failed for maxcube: Invalid config.

It’s probably something really obvious but I couldn’t find a solution online.