'List the available vpc offerings
:rtype ``list`` of :class:`CloudStackVPCOffering`'

def ex_list_vpc_offerings(self):

    res = self._sync_request(command='listVPCOfferings', method='GET')
    vpcoffers = res.get('vpcoffering', [])
    vpcofferings = []
    for vpcoffer in vpcoffers:
        vpcofferings.append(CloudStackVPCOffering(vpcoffer['name'], vpcoffer['displaytext'], vpcoffer['id'], self))
    return vpcofferings
