code: def summary(processors, metrics, context):
      
      # display aggregated metric values on language level
      def display_header(processors, before='', after=''):
          """Display the header for the summary results."""
          print(before, end=' ')
          for processor in processors:
              processor.display_header()
          print(after)
  
      def display_separator(processors, before='', after=''):
          """Display the header for the summary results."""
          print(before, end=' ')
          for processor in processors:
              processor.display_separator()
          print(after)
  
      def display_metrics(processors, before='', after='', metrics=[]):
          """Display the header for the summary results."""
          print(before, end=' ')
          for processor in processors:
              processor.display_metrics(metrics)
          print(after)
  
      summary = {}
      for m in metrics:
          lang = metrics[m]['language']
          has_key = lang in summary
          if not has_key:
              summary[lang] = {'file_count': 0, 'language': lang}
          summary[lang]['file_count'] += 1
          for i in metrics[m]:
              if i not in ['sloc', 'comments', 'mccabe']:  # include metrics to be used
                  continue
              if not has_key:
                  summary[lang][i] = 0
              summary[lang][i] += metrics[m][i]
  
      total = {'language': 'Total'}
      for m in summary:
          for i in summary[m]:
              if i == 'language':
                  continue
              if i not in total:
                  total[i] = 0
              total[i] += summary[m][i]
  
      print('Metrics Summary:')
  
      display_header(processors, 'Files', '')
      display_separator(processors, '-'*5, '')
      for k in sorted(summary.keys(), key=str.lower):
          display_metrics(processors, '%5d' %
                          summary[k]['file_count'], '', summary[k])
      display_separator(processors, '-'*5, '')
      display_metrics(processors, '%5d' % total['file_count'],
                      '', total)
docs: Print the summary