text: 
  class Singleton(type):
      """ A metaclass that creates a Singleton base class when called.
          
          Code Author: https://stackoverflow.com/users/500584/agf 
          From: https://stackoverflow.com/questions/6760685/creating-a-singleton-in-python
      """
      _instances = {}
      def __call__(cls, *args, **kwargs):
          if cls not in cls._instances:
              cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
          return cls._instances[cls]