title: Method not declared in a inherited class
body: <p>I have a class named UnitDeckCard. It inherits from DeckCard, which inherits from TextureRect. My issue is that, in the UnitDeckCard, I'm trying to define an onready var with a node from the scene:</p>
  <p><code>onready var cost_label = $CostLabel</code></p>
  <p>But then I received an error <code>The method &quot;get_node&quot; isn't declared in the current class</code></p>
  <p>I thought that, since, by inheritance, UnitDeckCard inherits from a Control class (TextureRect class), get_node method would be available, as Control inherits from Node (get_node is a Node method). As I undestand, my case would be something like that:</p>
  <p>UnitDeckCard &lt; DeckCard &lt; TextureRect &lt; Control &lt; CanvasItem &lt; <strong>Node</strong> &lt; Object.</p>
  <p>Why can't I use get_node method in UnitDeckCard?</p>