<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_hosts(self, hostIds):
 """ Adds a host to the cluster. @param hostIds: List of IDs of hosts to add to cluster. @return: A list of ApiHostRef objects of the new hosts that were added to the cluster @since: API v3 """

    hostRefList = [ApiHostRef(self._get_resource_root(), x) for x in hostIds]
    return self._post("hosts", ApiHostRef, True, data=hostRefList,
        api_version=3)