You can solve this by using local set as follows or using a Map < Id, Set < Id >>
as your
return value.
private Map < Id, List < Id >> getDbrToAccountMap(Set < Id > dbrIds) {
Map < Id, List < Id >> dbrAccountMap = neenter code herew Map < Id, List < Id >> ();
Set < String > alreadyExistSet = new Set < String > ();
List < Id > accountIds = new List < Id > ();
for (DBR_Group_Member__c member: [select Id, Contact__c, Contact__r.AccountId, DBR__c from DBR_Group_Member__c where DBR__c in : dbrIds]) {
if (dbrAccountMap.get() == null) {
dbrAccountMap.put(member.DBR__c, new List < Id > );
}
if (!alreadyExistSet.contains('' + member.DBR__c + member.Contact__r.AccountId)) {
dbrAccountMap.get(member.DBR__c).add(member.Contact__r.AccountId);
alreadyExistSet.add('' + member.DBR__c + member.Contact__r.AccountId);
}
}
return dbrAccountMap;
}