docs: def get_interface_nodes(self, time_slice=0):
          """
          Returns the nodes in the first timeslice whose children are present in the first timeslice.
  
          Parameters
          ----------
          time_slice:int
                  The timeslice should be a positive value greater than or equal to zero
  
          Examples
          --------
          >>> from pgmpy.models import DynamicBayesianNetwork as DBN
          >>> dbn = DBN()
          >>> dbn.add_nodes_from(['D', 'G', 'I', 'S', 'L'])
          >>> dbn.add_edges_from([(('D',0),('G',0)),(('I',0),('G',0)),(('G',0),('L',0)),(('D',0),('D',1))])
          >>> dbn.get_interface_nodes()
          [('D', 0)]
          """
          if not isinstance(time_slice, int) or time_slice < 0:
              raise ValueError("The timeslice should be a positive value greater than or equal to zero")
  
          return [(edge[0][0], time_slice) for edge in self.get_inter_edges()]