code: def __call__(cls, *args, **kwargs):
      """Returns singleton instance. A thread safe implementation."""
      if cls not in cls.__instances:
          # Enter critical section.
          with cls.__lock:
              # Check once again.
              if cls not in cls.__instances:
                  # Create a new object instance - one per class.
                  cls.__instances[cls] = super(Singleton, cls).__call__(
                      *args, **kwargs
                  )
      # Return the instance.
      return cls.__instances[cls]
  
label_desc: Use image node_id 1 for calling the Singleton obj's underlying member method code with example usage: obj.__call__(cls) and returns: cls