question: default Document putAll ( Iterable < Field > fields , Predicate < CharSequence > acceptableFieldNames ) { for ( Field field : fields ) { if ( acceptableFieldNames . test ( field . getName ( ) ) ) { setValue ( field . getName ( ) , field . getValue ( ) ) ; } } return this ; }
target:  Attempts to copy all of the acceptable fields from the source and set on this document, overwriting any existing values.