question: private void putNulls ( Map < String , Object > values , Set < String > valuesAddedinThisFrame ) { if ( attributes != null ) { for ( Node n : attributes ) { if ( n . multiValued ) { putANull ( n . fieldName , values , valuesAddedinThisFrame ) ; } } } if ( hasText && multiValued ) { putANull ( fieldName , values , valuesAddedinThisFrame ) ; } if ( childNodes != null ) { for ( Node childNode : childNodes ) { childNode . putNulls ( values , valuesAddedinThisFrame ) ; } } }
target:  A recursive routine that walks the Node tree from a supplied start pushing a null string onto every multiValued fieldName's List of values where a value has not been provided from the stream.