code: void format( LessParser parser, URL baseURL, ReaderFactory readerFactory, StringBuilder target,  @Nonnull Map<String, String> options ) {
          state.baseURL = baseURL;
          this.readerFactory = readerFactory;
          this.options = options;
          this.rewriteUrl = parseRewriteUrl();
          addVariables( parser.getVariables() );
          state.isReference = false;
  
          for( Formattable rule : parser.getRules() ) {
              rule.prepare( this );
          }
  
          for( Formattable rule : parser.getRules() ) {
              switch( rule.getType() ) {
                  case Formattable.REFERENCE_INFO:
                      state.isReference = ((ReferenceInfo)rule).isReference();
                      continue;
                  case Formattable.MIXIN:
                      ((Mixin)rule).appendSubRules( null, this );
                      break;
                  case Formattable.CSS_AT_RULE:
                      if( state.isReference ) {
                          continue;
                      }
                      //$FALL-THROUGH$
                  default:
                      rule.appendTo( this );
              }
          }
          removeVariables( parser.getVariables() );
  
          output = target;
          for( CssOutput result : state.results ) {
              result.appendTo( target, lessExtends, this );
          }
      }
docs: Format the a parsed less file.
  
  @param parser
  the parser result
  @param baseURL
  the URL of the less file
  @param readerFactory
  A factory for the readers for imports.
  @param target
  the output of the resulting string
  @param options
  some optional options, see constants for details