text: from .compat import iteritems, izip
  
  
  class SlotBase(object):
      """
      Base class for class using __slots__.
      If some args or kwargs are not given when initialize class,
      the value of them will be set with ``None``.
      """
      def __init__(self, *args, **kwargs):
          setted = set()
          kwargs_ = dict(izip(self.__slots__, args))
          kwargs_.update(kwargs)
          for key, value in iteritems(kwargs_):
              setattr(self, key, value)
              setted.add(key)
          for key in set(self.__slots__) - setted:
              setattr(self, key, None)
  