parameters: (self, group_key_start=1)
docstring: Initializes the object.
  
      Args:
        group_key_start: the starting integer of group key.
docstring_summary: Initializes the object.
docstring_tokens: Initializes the object .
function: def __init__(self, group_key_start=1):
      """Initializes the object.
  
      Args:
        group_key_start: the starting integer of group key.
      """
      self._group_key = group_key_start
      self._instance_key_table = {}
      self._lock = threading.Lock()
function_tokens: def __init__ ( self , group_key_start = 1 ) : self . _group_key = group_key_start self . _instance_key_table = { } self . _lock = threading . Lock ( )