code: Expression unpack( CssFormatter formatter ) {
          Expression unpack = this;
          do { // unpack packed expressions like parenthesis or variables
              if( unpack.getClass() == FunctionExpression.class && ((FunctionExpression)unpack).toString().isEmpty() ) { //Parenthesis
                  unpack = ((FunctionExpression)unpack).get( 0 );
                  continue;
              }
              if( unpack.getClass() == VariableExpression.class ) {
                  unpack = ((VariableExpression)unpack).getValue( formatter );
                  continue;
              }
              break;
          } while(true);
          return unpack;
      }
docs: Unpack this expression to return the core expression
  @param formatter the CCS target
  @return the core expression