code: def with_metaclass(meta, *bases):
      
      class _Metaclass(meta):
          """Inner class"""
          __call__ = type.__call__
          __init__ = type.__init__
  
          def __new__(cls, name, this_bases, attrs):
              if this_bases is None:
                  return type.__new__(cls, name, (), attrs)
              return meta(name, bases, attrs)
  
      return _Metaclass(str('temporary_class'), None, {})
docs: A Python 2/3 compatible way of declaring a metaclass.
  
      Taken from `Jinja 2 <https://github.com/mitsuhiko/jinja2/blob/master/jinja2
      /_compat.py>`_ via `python-future <http://python-future.org>`_. License:
      BSD.
      Use it like this::
  
          class MyClass(with_metaclass(MyMetaClass, BaseClass)):
                  pass