public IEnumerable <StringField> GetField(SubjectGroup subjectGroup)
 {
     return(RelationIndex.Contains(subjectGroup.Id.ToInt())
         ? new List <StringField> {
         new StringField(FieldName, true.ToString(), Field.Store.YES)
     }
         : new List <StringField>());
 }
        public IEnumerable <DoubleField> GetField(SubjectGroup subjectGroup)
        {
            var subjectId = subjectGroup.Id.ToInt();

            return(RelationIndex.ContainsKey(subjectId)
                ? new List <DoubleField> {
                new DoubleField(FieldName, RelationIndex[subjectId], Field.Store.YES)
            }
                : new List <DoubleField>());
        }