docs: def create_tenant(self, tenant_id, retentions=None):
          """
          Create a tenant. Currently nothing can be set (to be fixed after the master
          version of Hawkular-Metrics has fixed implementation.
  
          :param retentions: A set of retention settings, see Hawkular-Metrics documentation for more info
          """
          item = { 'id': tenant_id }
          if retentions is not None:
              item['retentions'] = retentions
  
          self._post(self._get_tenants_url(), json.dumps(item, indent=2))