'Compute difference between create date and open date'

@api.depends('date_open')
def _compute_day_open(self):

    for lead in self.filtered((lambda l: l.date_open)):
        date_create = fields.Datetime.from_string(lead.create_date)
        date_open = fields.Datetime.from_string(lead.date_open)
        lead.day_open = abs((date_open - date_create).days)
