public function traverse_build( $fields = null, $params = null ) {

		if ( null === $fields ) {
			$fields = $this->fields;
		}

		$feed = array();

		foreach ( $fields as $field => $data ) {
			if ( ! is_array( $data ) ) {
				$field = $data;
			}

			if ( ! isset( $_GET[ 'filter_' . $field ] ) ) {
				continue;
			}

			$field_value = pods_v( 'filter_' . $field, 'get', false, true );

			if ( ! empty( $field_value ) || 0 < strlen( $field_value ) ) {
				$feed[ 'traverse_' . $field ] = array( $field );
			}
		}

		return $feed;
	}