AttributeError: 'NoneType' object has no attribute '_name'

Hello, I am a French student. I want test mymod, for workflow. But I have this error : AttributeError: 'NoneType' object has no attribute '_name' mymod.py # -*- coding: utf-8 -*- from osv import fields, osv def mymod_new(self, cr, uid, ids): self.write(cr, uid, ids, { 'state' : 'new' }) return True def mymod_assigned(self, cr, uid, ids): self.write(cr, uid, ids, { 'state' : 'assigned' }) return True def mymod_negotiation(self, cr, uid, ids): self.write(cr, uid, ids, { 'state' : 'negotiation' }) return True def mymod_won(self, cr, uid, ids): self.write(cr, uid, ids, { 'state' : 'won' }) return True def mymod_lost(self, cr, uid, ids): self.write(cr, uid, ids, { 'state' : 'lost' }) return True class mymod(osv.osv): _name = "mymod.mymod" _description = "mymod" _columns = { 'name' : fields.char("names",), 'state': fields.selection([ ('new','New'), ('assigned','Assigned'), ('negotiation','Negotiation'), ('won','Won'), ('lost','Lost')], 'Stage', readonly=True), } mymod_workflow.xml mymod.wkfmymod.mymodTrueTruenewfunctionmymod_new()assignedfunctionmymod_assigned()negotiationfunctionmymod_negotiation()wonfunctionmymod_won()Truelostfunctionmymod_lost()Truemymod_assignedmymod_negotiationmymod_wonmymod_lost mymod_view.xmlmymod.form I think ERROR IT'S HERE :mymod.mymodform

Thanks for your help.