docstr: Calculate the difference of two dictionary along their keys.
  The result is values in d_after minus values in d_before.
docstr_tok: ["Calculate","the","difference","of","two","dictionary","along","their","keys",".","The","result","is","values","in","d_after","minus","values","in","d_before","."]
code: def _diff(d_after, d_before):
      """Calculate the difference of two dictionary along their keys.
      The result is values in d_after minus values in d_before.
      """
      ret = {}
      key_after, key_before = set(d_after), set(d_before)
      for k in key_before & key_after:
          tmp = d_after[k] - d_before[k]
          if tmp:
              ret[k] = d_after[k] - d_before[k]
      for k in key_after - key_before:
          ret[k] = d_after[k]
      for k in key_before - key_after:
          ret[k] = -d_before[k]
      return ret
  
imports: import tvm
  import tvm.relay
  from tvm.relay.testing import resnet
  from tvm.contrib.download import download_testdata
  from tvm.relay.build_module import bind_params_by_name
  from tvm.ir.instrument import PassTimingInstrument, pass_instrument
  from pprint import pprint
label_desc: Use image node_id 8 for calling the RelayCallNodeDiffer obj's underlying member method code with example usage: obj._diff(d_after, d_before) and returns: ret