// boolean predicate indicating if the loop is still executing. This is used to
// drive the gradient computation for the while loop associated with
// `while_ctx`.
Status AddBackPropLoopCounter(WhileContext* while_ctx, const Output& loop_count,
                              const Scope& scope,
                              Output* backprop_execution_pred) {
  // Create while loop:
  //   n = loop_count