'Returns a generator of tuples like dict.items(), where the key is
resolved (as a string) and the values are still lazy contexts.'

def exact_key_items(self):

    for (key_node, value) in self._items():
        for key in self._defining_context.eval_node(key_node):
            if precedence.is_string(key):
                (yield (key.obj, context.LazyTreeContext(self._defining_context, value)))
