docs: def global_registry(self):
          """Global Registry
  
  
          NOTE: Parses main conf files (/etc/fwissr/fwissr.json
              and ~/.fwissr/fwissr.json)
  
          then uses 'fwissr_sources' setting to setup additional sources
  
          Example of /etc/fwissr/fwissr.json file:
  
           {
             'fwissr_sources': [
               { 'filepath': '/mnt/my_app/conf/' },
               { 'filepath': '/etc/my_app.json' },
               { 'mongodb': 'mongodb://db1.example.net/my_app',
                   'collection': 'config', 'refresh': true },
             ],
             'fwissr_refresh_period': 30,
          }
          access global registry with Fwissr['/foo/bar']
          """
          if self._global_registry is None:
              if 'fwissr_refresh_period' in self.main_conf:
                  result = Registry(
                      refresh_period=self.main_conf['fwissr_refresh_period'])
              else:
                  result = Registry()
  
              if (os.path.exists(self.main_conf_path) or
                      os.path.exists(self.main_user_conf_path)):
  
                  if os.path.exists(self.main_conf_path):
                      result.add_source(
                          Source.from_settings(
                              {'filepath': self.main_conf_path}))
  
                  if os.path.exists(self.main_user_conf_path):
                      result.add_source(
                          Source.from_settings(
                              {'filepath': self.main_user_conf_path}))
  
                  if 'fwissr_sources' in self.main_conf:
                      for source in self.main_conf['fwissr_sources']:
                          result.add_source(Source.from_settings(source))
  
              self._global_registry = result
          return self._global_registry