T A reference to the live component data. Like VisualElement.GetComponent, the reference is valid until a component is added to or removed from this element.
Returns a reference to the component of type T attached to this
element. If the component is not attached yet, it is added first.
When the component is already attached, this method behaves exactly like VisualElement.GetComponent and the component data is not changed. When it is not attached, a new component is created and added the same way as VisualElement.AddComponent. The new component is created with the type's UxmlCreateInstanceMethodAttribute method when the type has one, otherwise with default values.