class_docstr: Metaclass to make a metaclassed class a singleton
class_docstr_tok: ["Metaclass","to","make","a","metaclassed","class","a","singleton"]
code: def __call__(cls, *args, **kwargs):
      if cls._singleton is None:
          cls._singleton = super(MetaSingleton, cls).__call__(
              *args, **kwargs
          )
  
      return cls._singleton
  
file_path: backtrader/backtrader/store.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import collections
  from backtrader.metabase import MetaParams
  from backtrader.utils.py3 import with_metaclass
label_desc: Use image node_id 2 for calling the MetaSingleton obj's underlying member method code with example usage: obj.__call__(cls) and returns: cls