protected function buildButton()
    {
        list($content, $attr) = $this->button;

        $mid = $this->attr['id'];

        $attr = $this->escaper->attr(
            array_merge_recursive(
                $attr,
                [
                    'type'        => 'button',
                    'data-toggle' => 'modal',
                    'data-target' => "#{$mid}"
                ]
            )
        );

        $this->html .= $this->indent(0, "<button $attr>");
        $this->html .= $this->indent(1, $content);
        $this->html .= $this->indent(0, '</button>');
    }