code: def deltas_buffer_wref():
      # returns 2 empty DeltasTree object for
      # tests that need to allocate shared
      # deltas buffers for 2 models
      # (one test, one reference)
      return (DeltasTree(), DeltasTree())
  
imports: import itertools
  import numpy
  import pytest
  import re
  import os
  import sys
  from neon.backends import gen_backend
  from neon.backends.nervanacpu import NervanaCPU
  from neon.layers.container import DeltasTree
label_desc: Use image node_id 16 for calling a global function with example usage: deltas_buffer_wref() and returns: DeltasTree,  DeltasTree