Return a portgroup object corresponding to the portgroup name on the dvs

    :param dvs: DVS object
    :param portgroup_name: Name of portgroup to return
    :return: Portgroup object

def _get_dvs_uplink_portgroup(dvs, portgroup_name):
    '''
    Return a portgroup object corresponding to the portgroup name on the dvs

    :param dvs: DVS object
    :param portgroup_name: Name of portgroup to return
    :return: Portgroup object
    '''
    for portgroup in dvs.portgroup:
        if portgroup.name == portgroup_name:
            return portgroup

    return None