   end
 
   @doc false
-  def config do
+  def config() do
     case Application.get_env(:shippex, :carriers, :not_found) do
       :not_found -> raise InvalidConfigError, "Shippex config not found"
 

  Fetches the label for `shipment` for a specific `Service`. The `service`
  module contains the `Carrier` and selected delivery speed.

      Shippex.fetch_label(shipment, service)
  """
  @spec fetch_label(Shipment.t, Service.t) :: {atom, Label.t}
  def fetch_label(%Shipment{} = shipment, %Service{carrier: carrier} = service) do
    Carrier.module(carrier).fetch_label(shipment, service)
  end

  @doc """

      Shippex.env #=> :dev
  """
  @spec env() :: atom
  def env() do
    case Application.get_env(:shippex, :env, :dev) do
      e when e in [:dev, :prod] -> e
      _ -> raise InvalidConfigError, "Shippex env must be either :dev or :prod"
