Update return type form self to static

Author: Admin

src/Models/BaseModel.php

@@ -112,7 +112,7 @@ public function getPrimaryKeyIdentifierAttribute(): string
         ));
     }
 
-    public function appendIndexRequiredOnFilteringAttribute(bool $appendIndex = true): self
+    public function appendIndexRequiredOnFilteringAttribute(bool $appendIndex = true): static
     {
         return $appendIndex && $this->indexRequiredOnFiltering ? $this->append(['index_required_on_filtering']) : $this;
     }