question: public static String unexpand ( CharSequence self , int tabStop ) { if ( self . length ( ) == 0 ) return self . toString ( ) ; StringBuilder builder = new StringBuilder ( ) ; for ( String line : new LineIterable ( self ) ) { builder . append ( unexpandLine ( ( CharSequence ) line , tabStop ) ) ; builder . append ( "\n" ) ; } if ( self . charAt ( self . length ( ) - 1 ) != '\n' ) { builder . deleteCharAt ( builder . length ( ) - 1 ) ; } return builder . toString ( ) ; }
target:  Replaces sequences of whitespaces with tabs.