class_docstr: The base class for recommendation models in Analytics Zoo.
class_docstr_tok: ["The","base","class","for","recommendation","models","in","Analytics","Zoo","."]
code: def _to_tuple_rdd(feature_rdd):
      assert isinstance(
          feature_rdd, RDD
      ), "feature_rdd should be RDD of UserItemFeature"
      return feature_rdd.map(lambda x: (x.user_id, x.item_id, x.sample))
  
imports: import sys
  from pyspark import RDD
  from zoo.models.common import *
  from zoo.common.utils import callZooFunc
label_desc: Use image node_id 4 for calling the Recommender obj's underlying member method code with example usage: obj._to_tuple_rdd(feature_rdd) and returns: feature_rdd