'Render an item
@param tbody: the TBODY or TABLE to append to
@param item: the item dict
@param level: the grouping level'

def html_render_item(self, tbody, item, level=0):

    columns = self.data['c']
    cells = []
    for column in columns:
        cells.append(TD(item.get(column, '')))
    tbody.append(TR(cells, _class=('gi-item    gi-level-%s' % level)))
