code: def traverse_nodes(self, node_set, depth=0):
          
  
          tab = "  "
          result = list()
          for n in node_set:
              repr = (
                  n
                  if self.nodes[n]["type"] == "variable"
                  else f"{n}{inspect.signature(self.nodes[n]['lambda_fn'])}"
              )
  
              result.append(f"{tab * depth}{repr}")
              result.extend(
                  self.traverse_nodes(self.successors(n), depth=depth + 1)
              )
          return result
docs: BFS traversal of nodes that returns name traversal as large string.
  
          Args:
              node_set: Set of input nodes to begin traversal.
              depth: Current traversal depth for child node viewing.
  
          Returns:
              type: String containing tabbed traversal view.