code: @JsonIgnore
      public void setNullResultsObject(final Set<IPersonAttributes> nullResultsObject) {
          if (nullResultsObject == null) {
              throw new IllegalArgumentException("nullResultsObject may not be null");
          }
  
          this.nullResultsObject = nullResultsObject;
      }
docs: Used to specify the placeholder object to put in the cache for null results. Defaults to a minimal Set. Most
  installations will not need to set this.
  
  @param nullResultsObject the nullResultsObject to set