class_docstr: Base class for models
class_docstr_tok: ["Base","class","for","models"]
docstr: Subclass will implement this.
docstr_tok: ["Subclass","will","implement","this","."]
code: def _build_graph(self):
      """Subclass will implement this."""
      pass
  
imports: from os.path import join
  import abc
  import time
  import os
  import numpy
  import tensorflow
  from recommenders.models.deeprec.deeprec_utils import cal_metric
label_desc: Use image node_id 2 for calling the BaseModel obj's underlying member method code with example usage: obj._build_graph() without return types