docstr: Returns all the nodes in the graph as a cudf.Series, in order of appearance
  in the edgelist (source column first, then destination column).
  If multi columns vertices, return a cudf.DataFrame.
docstr_tok: ["Returns","all","the","nodes","in","the","graph","as","a","cudf.Series",",","in","order","of","appearance","in","the","edgelist","(","source","column","first",",","then","destination","column",")",".","If","multi","columns","vertices",",","return","a","cudf.DataFrame","."]
code: def nodes(self):
      """
      Returns all the nodes in the graph as a cudf.Series, in order of appearance
      in the edgelist (source column first, then destination column).
      If multi columns vertices, return a cudf.DataFrame.
      """
      if self.edgelist is not None:
          df = self.edgelist.edgelist_df
          if self.properties.renumbered:
              df = self.renumber_map.df_internal_to_external.drop(
                  columns="id"
              )
  
              if len(df.columns) > 1:
                  return df
              else:
                  return df[df.columns[0]]
          else:
              return (
                  cudf.concat(
                      [
                          df[simpleGraphImpl.srcCol],
                          df[simpleGraphImpl.dstCol],
                      ]
                  )
                  .drop_duplicates()
                  .reset_index(drop=True)
              )
      if self.adjlist is not None:
          return cudf.Series(np.arange(0, self.number_of_nodes()))
  
imports: from cugraph.structure import graph_primtypes_wrapper
  from cugraph.structure.graph_primtypes_wrapper import Direction
  from cugraph.structure.symmetrize import symmetrize
  from cugraph.structure.number_map import NumberMap
  import cugraph.dask.common.mg_utils
  import cudf
  import dask_cudf
  import cugraph.dask.comms.comms
  import pandas
  import numpy
  import warnings
  from cugraph.dask.structure import replication
  from typing import Union, Dict
  from pylibcugraph import get_two_hop_neighbors, select_random_vertices
  from pylibcugraph import ResourceHandle, GraphProperties, SGGraph
label_desc: Use image node_id 34 for calling the simpleGraphImpl obj's underlying member method code with example usage: obj.nodes() and returns: cudf, cudf, df, df