':rtype ``list`` of :class:`NodeSize`'

def list_sizes(self, location=None):

    szs = self._sync_request(command='listServiceOfferings', method='GET')
    sizes = []
    for sz in szs['serviceoffering']:
        extra = {'cpu': sz['cpunumber']}
        sizes.append(NodeSize(sz['id'], sz['name'], sz['memory'], 0, 0, 0, self, extra=extra))
    return sizes
