How to add Map of id list of object in apex

     Map<Id,list<Lead>> affliateToLeadsMap = new Map<Id,list<Lead>>();
        for(Lead ld: [SELECT Id, CreatedDate, FirstName, LastName, Email, Status, Affiliate__c FROM Lead WHERE Affiliate__r.Type =: ACC_TYPE_AFF_BROKET_PARTNER AND  Status =: Constant.LEAD_STATUS_PRE_APPROVED AND createdDate > YESTERDAY ]){
            if(affliateToLeadsMap.containsKey(ld.Affiliate__c)){
                affliateToLeadsMap.get(ld.Affiliate__c).add(ld);
            }else{
                affliateToLeadsMap.put(ld.Affiliate__c, new list<Lead>{ld});
            }
        }