Alchemy.Events.on_bulk_delete

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

on_bulk_delete(func)

(macro)

Registers a handle triggering whenever messages get bulk deleted from a channel.

args : [snowflake], snowflake

Receives a list of message ids that were deleted, and the channel they were deleted from.