public function add_orphaned_column( $key ) {

		// Bail if the field is already part of the columns
		if ( $this->column_exists( $key ) ) {
			return false;
		}

		// Add the column with a format that
		// can be processed by the exporter
		$field          = array();
		$field['type']  = 'orphaned';
		$field['slug']  = $key;
		$field['label'] = ucwords( str_replace( '-', ' ', str_replace( '_', ': ', $key ) ) );

		// Add the field to the columns
		$this->meta_columns[] = (object) $field;

		return $field;

	}