def sibseq(node):
    """
        | Get the sequence-number of siblings(share the same parent)
        
        :param  lxml.etree._Element node: 
            lxml-etree-element
        :return int: 
            the sequence-number of siblings
        
        ::

            html_str = ""\"
            <html>
                <head>
                </head>
                <body>
                    <div-out-1>
                        <div id="0">b0</div>
                        <div id="1">b1</div>
                        <div id="2">b2</div>
                        <div id="3">b3</div>
                    </div-out-1>
                    <div-out-2>
                        <li id="0">l0</li>
                        <li id="1">l1</li>
                        <li id="2">l2</li>
                        <li id="3">l3</li>
                    </div-out-2>
                </body>
            </html>
            ""\"
            
            root = LXHTML(html_str)
            ele = engine.xpath(root,"//body/div-out-1/div",2)
            ele.text
            # 'b2'
            engine.sibseq(ele)
            # 2
        
    """
    p = node.getparent()
    if p == None:
        return 0
    else:
        childs = p.getchildren()
        total = childs.__len__()
        for i in range(0, total):
            if node == childs[i]:
                curr_seq = i
                return curr_seq
            else:
                pass
