Alchemy.Events.on_reaction_remove

You're seeing just the macro on_reaction_remove, go back to Alchemy.Events module for more information.
Link to this macro

on_reaction_remove(func)

(macro)

Registers a handle triggering whenever a user deletes a reaction to a message.

args : snowflake, snowflake, snowflake, %{"animated" => boolean, "id" => integer, "name" => String.t}

Receives the id of the user that reacted/deleted, the channel_id where it happened, the message_id and the emoji