'Get the item\'s Y unit.'

def get_graph_yunit(self, item, pre_label=''):

    try:
        unit = ('    (%s)' % item['y_unit'])
    except KeyError:
        unit = ''
    if (pre_label == ''):
        label = ''
    else:
        label = pre_label.split('_')[0]
    return ('%s%s' % (label, unit))
