   @doc """
   Extend presence information with additional data.
 
-  When `c:list/2` is used to list all presences of the given `topic`, this
+  When `c:list/1` is used to list all presences of the given `topic`, this
   callback is triggered once to modify the result before it is broadcasted to
   all channel subscribers. This avoids N query problems and provides a single
   place to extend presence metadata. You must return a map of data matching the


  ## Examples

  Uses the same data format as `c:list/2`, but only
  returns metadata for the presences under a topic and key pair. For example,
  a user with key `"user1"`, connected to the same chat room `"room:1"` from two
  devices, could return:

        leaves: %{"456" => %{metas: [%{status: "online", phx_ref: ...}]}}
      },

  See `c:list/1` for more information on the presence data structure.

  ## Fetching Presence Information

