code: def load_instackenv(self):
          
          self.add_environment_file(user='stack', filename='stackrc')
          self.run('openstack baremetal import --json instackenv.json', user='stack')
          ironic_node_nbr = 0
          count_cmd = 'jq -M "{filter}|length" /home/stack/instackenv.json'
          # Nodes are either in the .nodes list or at the root of the document
          for f in ['.nodes', '.']:
              try:
                  ironic_node_nbr = int(
                      self.run(count_cmd.format(filter=f), user='stack')[0])
              except ValueError:
                  pass
              if ironic_node_nbr > 0:
                  break
          self._wait_for_ironic_nodes(ironic_node_nbr)
          # register association with the newly created ironic nodes and the
          # existing barematal nodes in the factory
          self.baremetal_factory.set_ironic_uuid(self.list_nodes())
          self.run('openstack baremetal configure boot', user='stack')
docs: Load the instackenv.json file and wait till the ironic nodes are ready.
          TODO(Gonéri): should be splitted, write_instackenv() to generate the
          instackenv.json and instackenv_import() for the rest.