'Get a list of port identifiers from a port group.
:param array: the array serial number
:param portgroup: the name of the portgroup
:returns: list of port ids, e.g. [\'FA-3D:35\', \'FA-4D:32\']'

def get_port_ids(self, array, portgroup):

    portlist = []
    portgroup_info = self.get_portgroup(array, portgroup)
    if portgroup_info:
        port_key = portgroup_info['symmetrixPortKey']
        for key in port_key:
            port = key['portId']
            portlist.append(port)
    return portlist
