code: def create_instances(configuration):
      
      instances = {}
      for methods in configuration.itervalues():
          for element in methods.itervalues():
              if not isinstance(element, tuple):
                  continue
              cls, _ = element
              if cls not in instances:
                  instances[cls] = cls()
      return instances
docs: Create necessary class instances from a configuration with no argument to the constructor
  
      :param dict configuration: configuration dict like in :attr:`~pyextdirect.configuration.Base.configuration`
      :return: a class-instance mapping
      :rtype: dict