public function _and($column, $value = null) {
        if (!is_array($column)) {
            $column = array($column => $value);
        }

        $this->query['where'][count($this->query['where']) - 1] = array_merge(
            $this->query['where'][count($this->query['where']) - 1],
            $column
        );

        return $this;
    }