code: func (p PhysicalIndexLookUpReader) Init(ctx sessionctx.Context) *PhysicalIndexLookUpReader {
  	p.basePhysicalPlan = newBasePhysicalPlan(ctx, TypeIndexLookUp, &p)
  	p.TablePlans = flattenPushDownPlan(p.tablePlan)
  	p.IndexPlans = flattenPushDownPlan(p.indexPlan)
  	p.schema = p.tablePlan.Schema()
  	return &p
  }
docs: // Init initializes PhysicalIndexLookUpReader.