docs: def bases_walker(cls):
      """
      Loop through all bases of cls
  
      >>> str = u'hai'
      >>> for base in bases_walker(unicode):
      ...     isinstance(str, base)
      True
      True
  
      :param cls: The class in which we want to loop through the base classes.
      """
      for base in cls.__bases__:
          yield base
          for more in bases_walker(base):
              yield more