Alchemy.Events.on_member_update

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

on_member_update(func)

(macro)

Registers a handle triggering when the status of a member changes in a guild.

args : Alchemy.Guild.Guild.member, snowflake

Receives the member that was updated, and the guild they belong to.