retrieve our attributes

def get_attrs(self):
        """ retrieve our attributes """
        self.non_index_axes = []
        self.nan_rep = None
        self.levels = []

        self.index_axes = [a.infer(self)
                           for a in self.indexables if a.is_an_indexable]
        self.values_axes = [a.infer(self)
                            for a in self.indexables if not a.is_an_indexable]
        self.data_columns = [a.name for a in self.values_axes]