fix: fixed deprecated errors related to return types

Author: PooyaRaki

src/Spec/v3/AbstractObject.php

@@ -56,7 +56,7 @@ final public function __set($name, $value)
      *
      * @return bool
      */
-    final public function offsetExists($offset)
+    final public function offsetExists($offset): bool
     {
         return isset($this->$offset);
     }
@@ -66,7 +66,7 @@ final public function offsetExists($offset)
      *
      * @return mixed
      */
-    final public function offsetGet($offset)
+    final public function offsetGet($offset): mixed
     {
         return $this->$offset;
     }
@@ -75,15 +75,15 @@ final public function offsetGet($offset)
      * @param string $offset
      * @param mixed  $value
      */
-    final public function offsetSet($offset, $value)
+    final public function offsetSet($offset, $value): void
     {
         $this->$offset = $value;
     }
 
     /**
      * @param string $offset
      */
-    final public function offsetUnset($offset)
+    final public function offsetUnset($offset): void
     {
         unset($this->$offset);
     }
@@ -203,7 +203,7 @@ public function toYaml(
      *
      * @return array|stdClass
      */
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         $properties = $this->toArray();
         return empty($properties) ? new stdClass() : $properties;