code: def get_node(self, node_id, project_id=None):
          
  
          if project_id:
              # check the project_id exists
              project = ProjectManager.instance().get_project(project_id)
  
          try:
              UUID(node_id, version=4)
          except ValueError:
              raise aiohttp.web.HTTPBadRequest(text="Node ID {} is not a valid UUID".format(node_id))
  
          if node_id not in self._nodes:
              raise aiohttp.web.HTTPNotFound(text="Node ID {} doesn't exist".format(node_id))
  
          node = self._nodes[node_id]
          if project_id:
              if node.project.id != project.id:
                  raise aiohttp.web.HTTPNotFound(text="Project ID {} doesn't belong to node {}".format(project_id, node.name))
  
          return node
docs: Returns a Node instance.
  
          :param node_id: Node identifier
          :param project_id: Project identifier
  
          :returns: Node instance