class_docstr: This class handles the parser event from opt_parser.
  When a target statement is matched, an event is triggered,
  we collected necessary information from this event and construct
  the branches as what we want to understand.
code: def rf_mul_add(self, op_list):
      return op_list
  
imports: import nnabla
label_desc: Use image node_id 10 for calling the OptimizerBuilder obj's underlying member method code with example usage: obj.rf_mul_add(op_list) and returns: op_list