Discord.SortedSet.NifBridge.find_index

You're seeing just the function find_index, go back to Discord.SortedSet.NifBridge module for more information.

find_index(set, item)

find_index(set :: Discord.SortedSet.t(), item :: any()) ::
  Discord.SortedSet.Types.nif_find_result()
  | Discord.SortedSet.Types.common_errors()

Finds the index of the specified item