docs: def get_statistics(prefix=''):
      """
      Get statistics for message codes that start with the prefix.
  
      prefix='' matches all errors and warnings
      prefix='E' matches all errors
      prefix='W' matches all warnings
      prefix='E4' matches all errors that have to do with imports
      """
      stats = []
      keys = options.messages.keys()
      keys.sort()
      for key in keys:
          if key.startswith(prefix):
              stats.append('%-7s %s %s' %
                           (options.counters[key], key, options.messages[key]))
      return stats