'Render a group of rows
@param tbody: the TBODY or TABLE to append to
@param group: the group dict
@param level: the grouping level'

def html_render_group(self, tbody, group, level=0):

    if (self.group_headers and (level > 0)):
        self.html_render_group_header(tbody, group, level=level)
    subgroups = group.get('d')
    items = group.get('i')
    if subgroups:
        for subgroup in subgroups:
            self.html_render_group(tbody, subgroup, level=(level + 1))
    elif items:
        for item in items:
            self.html_render_item(tbody, item, level=level)
    if (level > 0):
        self.html_render_group_footer(tbody, group, level=level)
