code: def build_header(self, plugin, attribute, stat):
          
          line = ''
  
          if attribute is not None:
              line += '{}.{}{}'.format(plugin, attribute, self.separator)
          else:
              if isinstance(stat, dict):
                  for k in stat.keys():
                      line += '{}.{}{}'.format(plugin,
                                               str(k),
                                               self.separator)
              elif isinstance(stat, list):
                  for i in stat:
                      if isinstance(i, dict) and 'key' in i:
                          for k in i.keys():
                              line += '{}.{}.{}{}'.format(plugin,
                                                          str(i[i['key']]),
                                                          str(k),
                                                          self.separator)
              else:
                  line += '{}{}'.format(plugin, self.separator)
  
          return line
docs: Build and return the header line