docs: def add_node(self, node, **kwargs):
          """
          Add a single node to the cluster graph.
  
          Parameters
          ----------
          node: node
              A node should be a collection of nodes forming a clique. It can be
              a list, set or tuple of nodes
  
          Examples
          --------
          >>> from pgmpy.models import ClusterGraph
          >>> G = ClusterGraph()
          >>> G.add_node(('a', 'b', 'c'))
          """
          if not isinstance(node, (list, set, tuple)):
              raise TypeError('Node can only be a list, set or tuple of nodes forming a clique')
  
          node = tuple(node)
          super(ClusterGraph, self).add_node(node, **kwargs)