Element_Type_Manager::unregister( string $slug )

	public function unregister( $slug ) {
		if ( ! $this->has( $slug ) ) {
			/* translators: %s: element type slug */
			return new Error( $this->get_prefix() . 'element_type_not_exist', sprintf( __( 'An element type with the slug %s does not exist.', 'torro-forms' ), $slug ), __METHOD__, '1.0.0' );
		}

		if ( isset( $this->default_element_types[ $slug ] ) ) {
			/* translators: %s: element type slug */
			return new Error( $this->get_prefix() . 'element_type_is_default', sprintf( __( 'The default element type %s cannot be unregistered.', 'torro-forms' ), $slug ), __METHOD__, '1.0.0' );
		}

		unset( $this->element_types[ $slug ] );

		return true;
	}