@classmethod
def from_iso(cls, iso):
    """Retrieve the first datacenter id associated to an ISO."""
    result = cls.list({'sort_by': 'id ASC'})
    dc_isos = {}
    for dc in result:
        if dc['iso'] not in dc_isos:
            dc_isos[dc['iso']] = dc['id']
    return dc_isos.get(iso)
