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 clone_func(self, op):
      for i in op.inputs:
          self.clone_variable(i)
      for o in op.outputs:
          self.clone_variable(o)
      self.get_unique_name(op.name)
      self.new_graph.functions[op.name] = op.clone(self.new_graph)
  
imports: import nnabla
label_desc: Use image node_id 12 for calling the OptimizerBuilder obj's underlying member method code with example usage: obj.clone_func(op) without return types