docs: def add_node(self, node, **attr):
          """
          Adds a single node to the Network
  
          Parameters
          ----------
          node: node
              A node can be any hashable Python object.
  
          Examples
          --------
          >>> from pgmpy.models import DynamicBayesianNetwork as DBN
          >>> dbn = DBN()
          >>> dbn.add_node('A')
          ['A']
          """
          super(DynamicBayesianNetwork, self).add_node((node, 0), **attr)