Can only deserialize JSON with ruby-client

I expect the returned value to be an XML object. however I can't achieve this because the accepted returned values are only JSON.
I am not clear so here the concerned code :

https://github.com/swagger-api/swagger-codegen/blob/master/modules/swagger-codegen/src/main/resources/ruby/api_client.mustache#L91

    # Deserialize the response to the given return type.
    #
    # @param [String] return_type some examples: "User", "Array[User]", "Hash[String,Integer]"
    def deserialize(response, return_type)
      body = response.body
      return nil if body.nil? || body.empty?

      # handle file downloading - save response body into a tmp file and return the File instance
      return download_file(response) if return_type == 'File'

      # ensuring a default content type
      content_type = response.headers['Content-Type'] || 'application/json'

      unless content_type.start_with?('application/json')
        fail "Content-Type is not supported: #{content_type}"
      end

      begin
        data = JSON.parse("[#{body}]", :symbolize_names => true)[0]
      rescue JSON::ParserError => e
        if %w(String Date DateTime).include?(return_type)
          data = body
        else
          raise e
        end
      end

      convert_to_type data, return_type
    end

This means that, (AFAIK) with the ruby client, I can only request an API that returns JSON.

Start with modules/swagger-codegen/src/main/resources/ruby/api_client.mustache at the deserialize method shown in the issue. Trace how response content types and returned values are handled, then verify the Ruby client can process an XML response without rejecting its Content-Type; no test file is named in the issue.