'List all assignments for a given volume/host/hostgroup.'

def list_assignments(self, vol=None, host=None, hg=None):

    cmd = RdxApiCmd(cmd_prefix=[VOLUMES, LIST_ASSIGN_CMD])
    if (vol is not None):
        cmd.set_argument(vol)
    elif (host is not None):
        cmd = RdxApiCmd(cmd_prefix=[HOSTS, LIST_ASSIGN_CMD])
        cmd.set_argument(host)
    elif (host is not None):
        cmd = RdxApiCmd(cmd_prefix=[HG_DIR, LIST_ASSIGN_CMD])
        cmd.set_argument(hg)
    return self._run_cmd(cmd)
