HI friends, I tried to create a mail alert through cron function, when there is no timesheet(hr.analytic.timesheet) entries not entered by last 2 days means.Here i posted my code that didnt worked,

from openerp.osv import osv, fields
class timesheet_mail_cron(osv.osv):
    _name='timesheet.mail.cron'
    _description = "Cron for Timesheet"
 
    def _cron_mail_timesheet(self, cr, uid, ids, context=None):
        today = fields.Date.from_string(fields.Date.today())
        timesheet_search = self.pool.get('hr.analytic.timesheet').search(cr, uid,[('date','<=', today )])
        print "timesheet search",timesheet_search
        timesheet = self.pool.get('hr.analytic.timesheet').browse(cr, uid, timesheet_search[0])
        print "timesheet",timesheet
        days = today - timesheet.date[0]
        print "days",days
        if days >= 2:
            template = self.pool.get('ir.model.data').get_object('asia_mail_alert_timesheet', 'email_timesheet_alert')
            template.send_mail(timesheet.id,force_send=True)
        return True

It throws error like -> TpeError: _cron_mail_timesheet() takes at least 4 arguments (3 given)

So plese anyone help me to resolve this issues.Thanks in advance