class_docstr: GraphStream is a class for delta automatical optimization
code: def __hint_op_type(self, pattern_name):
      assert (
          pattern_name in self.__hint_map
      ), "Pattern name({}) with hint op must be registered by \
                  function register_hint_op.".format(
          pattern_name
      )
      return self.__hint_map[pattern_name]
  
file_path: delta/gcompiler/python/delta_infer/optimizer.py
imports: from __future__ import absolute_import, division, print_function
  import os
  import sys
  from .subgraphs import *
  from .cpp import DeltaGraph, AutoOptimizer, RegisterPattern
label_desc: Use image node_id 3 for calling the GraphStream obj's underlying member method code with example usage: obj.__hint_op_type(pattern_name) and returns: self