question: static void checkCompatible ( FieldInfo fieldInfo ) { if ( fieldInfo . getDocValuesType ( ) != DocValuesType . NONE && fieldInfo . getDocValuesType ( ) != TYPE . docValuesType ( ) ) { throw new IllegalArgumentException ( "field=\"" + fieldInfo . name + "\" was indexed with docValuesType=" + fieldInfo . getDocValuesType ( ) + " but this type has docValuesType=" + TYPE . docValuesType ( ) + ", is the field really a Geo3DDocValuesField?" ) ; } }
target:  helper: checks a fieldinfo and throws exception if its definitely not a Geo3DDocValuesField 