For a bit of time Fabric API has been able to get the mod which has provided an entrypoint, rendering the getModId call redundant here https://github.com/MisterPeModder/ShulkerBoxTooltip/blob/1.16/src/main/java/com/misterpemodder/shulkerboxtooltip/api/ShulkerBoxTooltipApi.java#L117

The following method may be used to get the ModContainer + Entrypoint combination for your api:
https://github.com/FabricMC/fabric-loader/blob/master/src/main/java/net/fabricmc/loader/api/FabricLoader.java#L98