ExUssd.simulate

You're seeing just the macro simulate, go back to ExUssd module for more information.
Link to this macro

simulate(path, opts \\ [])

View Source (macro)

defmodule MyAppWeb.Router do

use Phoenix.Router
import ExUssd

scope "/", MyAppWeb do
  pipe_through [:browser]
  simulate "/simulator",
    menu: ExUssd.new(name: "Home", handler: MyHomeHandler),
    phone_numbers: ["254700100100", "254700200200", "254700300300"]
end

end