class_docstr: Model id helper.
  
  This helper is used to help `parl.Model` generate a new model id
  or register a given model id in a thread-safe way.
class_docstr_tok: ["Model","id","helper",".","This","helper","is","used","to","help","`","parl.Model","`","generate","a","new","model","id","or","register","a","given","model","id","in","a","thread-safe","way","."]
code: def __init__(self):
      self._registered_ids = set([])
      self.index = 0
      self.lock = threading.Lock()
  
imports: import threading
label_desc: Use image node_id 1 to create a new ModelHelper object from inherited base classes: object with example: obj = ModelHelper()