hi , i am new to openerp as well as python their exists an error while installing. please help me. my code was here.

from openerp.osv import osv, fields

class mymod(osv.Model):
    _name = 'mymod.mymod'    
    _columns = {
               'name': fields.char('Name', size = 100), 
               'dob': fields.date('Date of birth'),
               'father_name': fields.char('Father Name', size = 100),
               'state': fields.selection([
                                    ('new','New'),
                                    ('assigned','Assigned'),
                                    ('negotiation','Negotiation'),
                                    ('won','Won'),
                                    ('lost','Lost')], 'Stage', readonly=True),
                }

    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    

mymod()

i am studying the workflow example pls help me.. The error is IndentationError: unexpected indent