Magic setter: Set the property value.
$property_name: The name of the property to set; e.g., 'title' or 'name'.
$value: The value to set, or NULL to unset the property. Optionally, a typed data object implementing Drupal\Core\TypedData\TypedDataInterface may be passed instead of a plain value.
\InvalidArgumentException If a not existing property is set.
public function __set($property_name, $value);