class_docstr: Indexing edges for fast graph queries
  Sorted edges and represent edges in compressed style like csc_matrix or csr_matrix.
  
      Args:
          u: A list of node id to be compressed.
          v: A list of node id that are connected with u.
          num_nodes: The exactive number of nodes.
      
docstr: Return the sorted (u, v, eid) tuples.
          
docstr_tok: ["Return","the","sorted","(","u",",","v",",","eid",")","tuples","."]
code: def triples(self):
      """Return the sorted (u, v, eid) tuples."""
      return self._sorted_u, self._sorted_v, self._sorted_eid
  
imports: import os
  import json
  import copy
  import numpy
  import paddle
  from paddle.framework import core
  from pgl.utils import op
  import pgl.graph_kernel
  from pgl.utils.helper import check_is_tensor, to_paddle_tensor
label_desc: Use image node_id 7 for calling the EdgeIndex obj's underlying member method code with example usage: obj.triples() and returns: self,  self,  self