I am using elixir - phoenix - tesla - third party api

I want to send a post request to the third party api and send the same parameter with two different values, which in the third party api documentation stated that it is possible to do it. but i want to remove the square brackets around the parameter.

Currentley I get this is what is being sent:

green=yes&blue=no&shades[]=300&shades[]=199`

the api sends a response that Parameter 'shades' is missing

i want it like this:

green=yes&blue=no&shades=300&shades=199`

this is my code using Tesla — tesla v1.20.0

    {:ok, response} = request(method: :post, url: "/edit", body: [green: "yes", blue: "no", shades: [List.first(shades), List.last(shades)]])

it works when sending one parameter in a map like this:

%{
      "green" => "yes,
      "blue" => "no",
      "shades" => 300
  }

but again I need to send two values at the same time, how do I achieve this?