// - name of output tensor (in nested "add:z:0" format)
// dst is either:
// - output name (as it appears in FunctionDef)
// - <name_of_node>:<index_of_this_input_into_node> (this looks the same as
//      output tensor naming, but it the index is actually an input index)
struct EdgeSpec : public std::pair<string, string> {
  typedef std::pair<string, string> Base;

  // Inherit the set of constructors
  using Base::pair;

// which contains only the schemes under test.
//
// Without this additional step, when there are schemes available but the user
// only requests schemes that don't exist, first instantiation of the test would
// filter out all the user provided schemes (as they are not registered) but
// subsequent instantiations would return all registered schemes (since the
// vector with the user provided schemes is cleared).

  if (forward_input) {
    TFE_DeleteTensorHandle(n);
  }

  int num_retvals = 1;
  if (async) {
    // Enqueue dummy ops so we backlog async execution & actually test async.
    // This is usually unnecessary, but we've experienced the occasional test
    // failure when testing async mode with no explicit forwarding.
    for (int i = 0; i < 100000; ++i) {
      TFE_Op* add_op_dummy = AddOp(ctx, m, m);