ERROR modoo odoo.modules.registry: Failed to load registry

......

File "D:\odooproject\odoo13\odoo\fields.py", line 2927, in update_db

    raise UserError(_("No inverse field %r found for %r") % (self.inverse_name, self.comodel_name))

odoo.exceptions.UserError: ("未找到None对应的字段'subjects'", '')

I add a new Class 'Subject' to my module.

And ,when I open it, I get this error.

What‘s the cause of the error?

How can I do it?