docs: def add_nodes_from(self, nodes, **kwargs):
          """
          Add multiple nodes to the cluster graph.
  
          Parameters
          ----------
          nodes: iterable container
              A container of nodes (list, dict, set, etc.).
  
          Examples
          --------
          >>> from pgmpy.models import ClusterGraph
          >>> G = ClusterGraph()
          >>> G.add_nodes_from([('a', 'b'), ('a', 'b', 'c')])
          """
          for node in nodes:
              self.add_node(node, **kwargs)