Get list of mapping of ip address into a server id

def __IpsToServerIds(self):
    """ Get list of mapping of ip address into a server id"""
    master_instance = self.__GetMasterInstance()
    assert(master_instance)
    retval, response = self.__RunMaprCli('node list -columns id')
    ip_to_id = {}
    for line_num, line in enumerate(response.split('\n')):
      tokens = line.split()
      if len(tokens) == 3 and tokens[0] != 'id':        
        instance_id = tokens[0]
        ip = tokens[2]
        ip_to_id[ip] = instance_id
    return ip_to_id