 
   defp encode_body(no_attachments), do: Plug.Conn.Query.encode(no_attachments)
 
-  defp encode_variable(var) when is_map(var) or is_list(var), do: Swoosh.json_library().encode!(var)
+  defp encode_variable(var) when is_map(var) or is_list(var),
+    do: Swoosh.json_library().encode!(var)
+
   defp encode_variable(var), do: var
 end

  defp prepare_html(body, %{html_body: nil}), do: body
  defp prepare_html(body, %{html_body: html_body}), do: Map.put(body, :html, html_body)

  defp prepare_template(body, %{provider_options: %{template_name: template_name}}), do: Map.put(body, "template", template_name)

  defp prepare_template(body, _), do: body



  ## Provider options

  - `:custom_vars` (used to translate to `v:`, now `h:X-Mailgun-Variables`)
  - `:sending_options` (`o:`)
  - `:template_name` (template)
  - `:recipient_vars` (recipient-variables)
  - `:tags` (`o:tag`, was added in before `:sending_options`)

  ## Custom headers

