class Singleton(abc.ABCMeta, type): ‘:raw-latex:`\n `Singleton metaclass for ensuring only one instance of a class.:raw-latex:`n `’ _instances: Dict[(str, Any)] = {}

def __call__(self, *args, **kwargs):
    'Call method for the singleton metaclass.'
    if (self not in self._instances):
        self._instances[self] = super(Singleton, self).__call__(*args, **kwargs)
    return self._instances[self]