question: default Document putAll ( Map < ? extends CharSequence , Object > fields ) { if ( fields != null ) { for ( Map . Entry < ? extends CharSequence , Object > entry : fields . entrySet ( ) ) { set ( entry . getKey ( ) , entry . getValue ( ) ) ; } } return this ; }
target:  Sets on this object all key/value pairs from the supplied map. If the supplied map is null, this method does nothing.