get related_series from parse info.

        :param parse_info: Parsed info from html soup.

def _get_related_series(parse_info):
        """get related_series from parse info.

        :param parse_info: Parsed info from html soup.
        """
        seriesother_tags = [x for x in parse_info.select('h5.seriesother')]
        sibling_tag = [x for x in seriesother_tags if x.text == 'Related Series'][0]
        siblings_tag = list(sibling_tag.next_siblings)

        # filter valid tag
        # valid tag is all tag before following tag
        # <h5 class="seriesother">Recommendations</h5>
        valid_tag = []
        keypoint_found = False
        for x in siblings_tag:
            # change keypoint if condition match
            if x.name == 'h5' and x.attrs['class'] == ['seriesother']:
                    keypoint_found = True

            if not keypoint_found and x.strip is not None:
                if x.strip():
                    valid_tag.append(x)
            elif not keypoint_found:
                valid_tag.append(x)

        # only one item found and it is 'N/A
        if len(valid_tag) == 1:
            if valid_tag[0].strip() == 'N/A':
                return None

        # items are combination between bs4 and text
        # merge and return them as list of text
        if len(valid_tag) % 2 == 0:
            zipped_list = zip(valid_tag[::2], valid_tag[1::2])
            result = []
            for x in zipped_list:
                result.append('{} {}'.format(x[0].text, x[1]))
            return result

        raise ValueError("Valid tag isn't recognizeable.\n{}".format("\n".join(valid_tag)))