class_docstr: It represents the relationship between two items.
class_docstr_tok: ["It","represents","the","relationship","between","two","items","."]
code: def __reduce__(self):
      return Relation, (self.id1, self.id2, self.label)
  
imports: from bigdl.dllib.utils.common import *
  from bigdl.dllib.utils.file_utils import callZooFunc
  from bigdl.dllib.feature.dataset.dataset import DataSet
  from pyspark.serializers import CloudPickleSerializer
  import sys
  import math
  import warnings
  from bigdl.dllib.utils.log4Error import *
label_desc: Use image node_id 2 for calling the Relation obj's underlying member method code with example usage: obj.__reduce__() and returns: Relation,  self,  self,  self