@ VisibleForTesting final synchronized ImmutableSet < String > getAttributeKeys ( ) { if ( attributes == null ) { return ImmutableSet . of ( ) ; } ImmutableSet . Builder < String > builder = ImmutableSet . builder ( ) ; for ( Table . Cell < String , String , Object > cell : attributes . cellSet ( ) ) { builder . add ( cell . getRowKey ( ) + ' ' + cell . getColumnKey ( ) ) ; } return builder . build ( ) ; }
Returns the attribute keys contained in the attributes map for the file .