Resolve #3512812 "Adding and removing"

Closes #3512812

src/Entity/ImageDeriver.php

@@ -81,6 +81,10 @@ class ImageDeriver extends ConfigEntityBase implements EntityWithPluginCollectio
     $this->derivers[$plugin_id] = $configuration;
   }
 
+  public function setDerivers(array $derivers) {
+    $this->derivers = $derivers;
+  }
+
   public function removeDeriver(string $plugin_id) {
     unset($this->derivers[$plugin_id]);
   }