code: def ladder_graph(n, create_using=None):
      """Returns the Ladder graph of length n.
  
      This is two paths of n nodes, with
      each pair connected by a single edge.
  
      Node labels are the integers 0 to 2*n - 1.
  
      .. plot::
  
          >>> nx.draw(nx.ladder_graph(5))
  
      """
      G = empty_graph(2 * n, create_using)
      if G.is_directed():
          raise NetworkXError("Directed Graph not supported")
      G.add_edges_from(pairwise(range(n)))
      G.add_edges_from(pairwise(range(n, 2 * n)))
      G.add_edges_from((v, v + n) for v in range(n))
      return G
  
imports: import itertools
  import numbers
  import networkx
  from networkx.classes import Graph
  from networkx.exception import NetworkXError
  from networkx.utils import nodes_or_number, pairwise
label_desc: Use image node_id 12 for calling a global function with example usage: ladder_graph(n, create_using) and returns: G