curl --request GET \
  --url https://{apiBaseUrl}/v2/{sessionId}/resources/countries

const url = 'https://{apiBaseUrl}/v2/{sessionId}/resources/countries';
const options = {method: 'GET'};

fetch(url, options)
  .then(res => res.json())
  .then(json => console.log(json))
  .catch(err => console.error(err));

import requests

url = "https://{apiBaseUrl}/v2/{sessionId}/resources/countries"

response = requests.get(url)

print(response.text)

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://{apiBaseUrl}/v2/{sessionId}/resources/countries",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

using RestSharp;


var options = new RestClientOptions("https://{apiBaseUrl}/v2/{sessionId}/resources/countries");
var client = new RestClient(options);
var request = new RestRequest("");
var response = await client.GetAsync(request);

Console.WriteLine("{0}", response.Content);

HttpResponse<String> response = Unirest.get("https://{apiBaseUrl}/v2/{sessionId}/resources/countries")
  .asString();

{
  "countries": [
    {
      "isoAlpha2": "FR",
      "name": "France",
      "phoneContraint": {
        "isStrict": true,
        "cellPhoneRegex": "^0?(6|7)\\d{8}$",
        "nationalPrefix": "0",
        "internationalPrefix": "+33"
      }
    },
    {
      "isoAlpha2": "GQ",
      "name": "Equatorial Guinea",
      "phoneContraint": {
        "isStrict": false,
        "internationalPrefix": "+240"
      }
    },
    {
      "isoAlpha2": "CZ",
      "name": "Czech Republic",
      "phoneContraint": {
        "isStrict": false,
        "internationalPrefix": "+420"
      }
    }
  ]
}

{
  "code": "InvalidSessionId"
}

{
  "code": "InvalidUserAuthentication",
  "message": "<string>"
}