Fill One2many table in default_get method

@api.model
    def default_get(self, fields):
        res = super(Report, self).default_get(fields)
        if self._context.get('task_id', False):
            res['task_id'] = self._context['task_id']
            task = self.env['project.task'].browse(res['task_id'])
            brl = self.env['bm.report.lines']
            report_lines = []
            for l in task.pricing_ids:
                report_line = brl.create({
                    'pricing_id': l.pricing_id.id,
                    'amount': l.amount,
                    'labor_vol': l.labor_vol,
                    'mech_vol': l.mech_vol,
                })
                report_lines.append(report_line.id)
            res['lines_ids'] = report_lines