SubscriptionsTransportWS.OperationMessage.from_map

You're seeing just the function from_map, go back to SubscriptionsTransportWS.OperationMessage module for more information.

Build OperationMessage from incoming map

iex> %{"type" => "connection_init"} |> OperationMessage.from_map
%OperationMessage{id: nil, type: "connection_init", payload: nil}