Batch class to remove user from group, if the user is assigned to multiple group

userGroupRemoval.cls

global class userGroupRemoval implements Database.Batchable<sObject> {
	String query = 'Select Id from user where isActive = true';
	global Database.QueryLocator start(Database.BatchableContext BC) {
		return Database.getQueryLocator(query);
	}
   	global void execute(Database.BatchableContext BC, List<sObject> scope) {
   		List<user> userRecord = (List<user>)scope;
   		List<GroupMember> duplicateGroupId = new List<GroupMember>();
   		Set<Id> userId = new Set<Id>();
   		for(GroupMember gpm : [Select Id,userorGroupId from GroupMember where userorGroupId IN:userRecord]){
   			if(userId.contains(gpm.userorGroupId)){
   				duplicateGroupId.add(gpm);
   			}
   			userId.add(gpm.userorGroupId);
   		}
   		if(duplicateGroupId.size() > 0)
   		   delete duplicateGroupId;
	}
	global void finish(Database.BatchableContext BC) {
	}
}