code: public String extract(String html, CETR.Parameters parameters) {
          html = clearText(html); //preprocess the Document by removing irrelevant HTML tags and empty lines and break the document to its lines
          List<String> rows = extractRows(html); //
          
          List<Integer> selectedRowIds = selectRows(rows, parameters);
          
          StringBuilder sb = new StringBuilder(html.length());
          for(Integer rowId : selectedRowIds) {
              String row = rows.get(rowId);
              
              //extract the clear text from the selected row
              row = StringCleaner.removeExtraSpaces(HTMLParser.extractText(row));
              if(row.isEmpty()) {
                  continue;
              }
              sb.append(row).append(" ");
          }
          
          return sb.toString().trim();
      }
docs: Extracts the main content for an HTML page.
  
  @param html
  @param parameters
  @return