code: def get_by_ip(cls, ip):
          'Returns Host instance for the given ip address.'
          ret = cls.hosts_by_ip.get(ip)
          if ret is None:
              ret = cls.hosts_by_ip[ip] = [Host(ip)]
          return ref get_by_ip(cls, ip):
          'Returns Host instance for the given ip address.'
          ret = cls.hosts_by_ip.get(ip)
          if ret is None:
              ret = cls.hosts_by_ip[ip] = [Host(ip)]
          return ret
docs: Returns Host instance for the given ip address.