Alchemy.Events.on_DMChannel_create

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

on_DMChannel_create(func)

(macro)

Registers a handle triggering whenever a user starts a DM with the client.

args : Alchemy.Channel.dm_channel

As opposed to on_channel_create, this event gets triggered when a user starts a direct message with this client.

Examples

Events.on_DMChannel_create(:foo)
def foo(%DMChannel{recipients: [user|_]}) do
  IO.inspect user.name <> " just DMed me!"
end