code: def _get_instances_for_project(self, project_id):
          
          search_opts = {'marker': None,
                         'all_tenants': True,
                         'project_id': project_id}
          try:
              servers = self._novaclnt.servers.list(True, search_opts)
              LOG.debug('_get_instances_for_project: servers=%s', servers)
              return servers
          except nexc.Unauthorized:
              emsg = (_LE('Failed to get novaclient:Unauthorised '
                      'project_id=%(proj)s user=%(user)s'),
                      {'proj': self._project_id, 'user': self._user_name})
              LOG.exception(emsg)
              raise nexc.ClientException(emsg)
          except nexc.AuthorizationFailure as err:
              emsg = (_LE("Failed to get novaclient %s"))
              LOG.exception(emsg, err)
              raise nexc.ClientException(emsg % err)
docs: Return all instances for a given project.
  
          :project_id: UUID of project (tenant)