code: def expectation(self):
      return (
          self.src_data["expectation"] * self.dst_data["expectation"]
      ).sum(1)
  
imports: import collections
  import functools
  import io
  import os
  import warnings
  import dgl
  import numpy
  import scipy
  import torch
label_desc: Use image node_id 4 for calling the EdgeData obj's underlying member method code with example usage: obj.expectation() and returns: unknown