How to use the nexusformat.nexus.tree._readaxes function in nexusformat

def axis_box(self, axis=0):
        box = NXComboBox()
        for node in self.group.values():
            if node is not self.signal and self.check_axis(node, axis):
                box.addItem(node.nxname)
        if box.count() == 0:
            return None
        if 'axes' in self.signal.attrs:
            from nexusformat.nexus.tree import _readaxes
            default_axis = _readaxes(self.signal.axes)[axis]
        else:
            axes = self.group.nxaxes
            if axes is not None:
                default_axis = self.group.nxaxes[axis].nxname
            else:
                default_axis = None
        if default_axis:
            try:
                box.setCurrentIndex(box.findText(default_axis))
            except Exception:
                pass
        else:
            box.setCurrentIndex(0)
        return box