diff --git a/src/Sellix.php b/src/Sellix.php
index 9360f1b..9e770fa 100644
--- a/src/Sellix.php
+++ b/src/Sellix.php
@@ -4,101 +4,102 @@
 
 define("BASE_DIR", dirname(__FILE__));
 
-require_once BASE_DIR."/Blacklists/index.php";
-require_once BASE_DIR."/Whitelists/index.php";
-require_once BASE_DIR."/Categories/index.php";
-require_once BASE_DIR."/Coupons/index.php";
-require_once BASE_DIR."/Feedback/index.php";
-require_once BASE_DIR."/Orders/index.php";
-require_once BASE_DIR."/Groups/index.php";
-require_once BASE_DIR."/Products/index.php";
-require_once BASE_DIR."/Queries/index.php";
-require_once BASE_DIR."/Payments/index.php";
-require_once BASE_DIR."/Customers/index.php";
-require_once BASE_DIR."/Subscriptions/index.php";
-require_once BASE_DIR."/Exceptions/index.php";;
-require_once BASE_DIR."/Tests/index.php";
+require_once BASE_DIR . "/Blacklists/index.php";
+require_once BASE_DIR . "/Whitelists/index.php";
+require_once BASE_DIR . "/Categories/index.php";
+require_once BASE_DIR . "/Coupons/index.php";
+require_once BASE_DIR . "/Feedback/index.php";
+require_once BASE_DIR . "/Orders/index.php";
+require_once BASE_DIR . "/Groups/index.php";
+require_once BASE_DIR . "/Products/index.php";
+require_once BASE_DIR . "/Queries/index.php";
+require_once BASE_DIR . "/Payments/index.php";
+require_once BASE_DIR . "/Customers/index.php";
+require_once BASE_DIR . "/Subscriptions/index.php";
+require_once BASE_DIR . "/Exceptions/index.php";
+require_once BASE_DIR . "/Tests/index.php";
 
 class Sellix {
-  protected string $api_key;
-
-  use Blacklists;
-  use Whitelists;
-  use Categories;
-  use Groups;
-  use Coupons;
-  use Feedback;
-  use Orders;
-  use Products;
-  use Queries;
-  use Payments;
-  use Customers;
-  use Subscriptions;
-
-  static $API_ENDPOINT = 'https://dev.sellix.io/v1';
-
-  public function __construct(string $api_key, string $merchant = NULL) {
-    $this->api_key = $api_key;
-    $this->merchant = $merchant;
-  }
-
-  private function handle_response($response, $key = NULL) {
-    if ($response->status != 200) {
-      throw new SellixException($response->error, $response->status);
-    } else {
-      if ($key === NULL) {
-        return NULL;
-      }
-
-      if (is_array($key) && array_key_exists("oneOf", $key)) {
-        $updated_response = new \stdClass();
-        foreach ($key["oneOf"] as $option) {
-          if (strpos($option, ",") !== false) {
-            foreach (explode(",", $option) as $key_option) {
-              if (property_exists($response->data, $key_option)) {
-                $updated_response->$key_option = $response->data->$key_option;
-              }
+    protected string $api_key;
+    protected ?string $merchant;
+
+    use Blacklists;
+    use Whitelists;
+    use Categories;
+    use Groups;
+    use Coupons;
+    use Feedback;
+    use Orders;
+    use Products;
+    use Queries;
+    use Payments;
+    use Customers;
+    use Subscriptions;
+
+    static $API_ENDPOINT = 'https://dev.sellix.io/v1';
+
+    public function __construct(string $api_key, ?string $merchant = NULL) {
+        $this->api_key = $api_key;
+        $this->merchant = $merchant;
+    }
+
+    private function handle_response($response, $key = NULL) {
+        if ($response->status != 200) {
+            throw new SellixException($response->error, $response->status);
+        } else {
+            if ($key === NULL) {
+                return NULL;
             }
-          } else if (property_exists($response->data, $option)) {
-            return $response->data->$option;
-          }
-        }
 
-        return $updated_response;
-      }
+            if (is_array($key) && array_key_exists("oneOf", $key)) {
+                $updated_response = new \stdClass();
+                foreach ($key["oneOf"] as $option) {
+                    if (strpos($option, ",") !== false) {
+                        foreach (explode(",", $option) as $key_option) {
+                            if (property_exists($response->data, $key_option)) {
+                                $updated_response->$key_option = $response->data->$key_option;
+                            }
+                        }
+                    } else if (property_exists($response->data, $option)) {
+                        return $response->data->$option;
+                    }
+                }
+
+                return $updated_response;
+            }
 
-      return $response->data->$key;
-    }
-  }
-
-  private function request($component, $action = "GET", $payload = NULL) {
-    $curl = curl_init();
-    
-    $headers = [
-      "Content-type: application/json",
-      "Authorization: Bearer " . $this->api_key
-    ];
-
-    if ($this->merchant) {
-      $headers[] = "X-Sellix-Merchant: ".$this->merchant;
+            return $response->data->$key;
+        }
     }
 
-    $curl_array = [
-      CURLOPT_RETURNTRANSFER => true,
-      CURLOPT_CUSTOMREQUEST => $action,
-      CURLOPT_URL => self::$API_ENDPOINT.$component,
-      CURLOPT_HTTPHEADER => $headers
-    ];
+    private function request($component, $action = "GET", $payload = NULL) {
+        $curl = curl_init();
 
-    if ($payload) {
-      $curl_array[CURLOPT_POSTFIELDS] = json_encode($payload);
-    }
+        $headers = [
+            "Content-type: application/json",
+            "Authorization: Bearer " . $this->api_key
+        ];
 
-    curl_setopt_array($curl, $curl_array);
+        if ($this->merchant) {
+            $headers[] = "X-Sellix-Merchant: " . $this->merchant;
+        }
+
+        $curl_array = [
+            CURLOPT_RETURNTRANSFER => true,
+            CURLOPT_CUSTOMREQUEST => $action,
+            CURLOPT_URL => self::$API_ENDPOINT . $component,
+            CURLOPT_HTTPHEADER => $headers
+        ];
+
+        if ($payload) {
+            $curl_array[CURLOPT_POSTFIELDS] = json_encode($payload);
+        }
+
+        curl_setopt_array($curl, $curl_array);
 
-    $response = curl_exec($curl);
-    curl_close($curl);
+        $response = curl_exec($curl);
+        curl_close($curl);
 
-    return json_decode($response);
-  }
-}
\ No newline at end of file
+        return json_decode($response);
+    }
+}