code: def deltas_buffer():
      # empty DeltasTree object for tests that need
      # to allocate shared deltas buffers
      return 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 15 for calling a global function with example usage: deltas_buffer() and returns: DeltasTree