docs: def validate_config(config):
          """Verify sanity for a :class:`.Config` instance.
  
          This will raise an exception in case conditions are not met, otherwise
          will complete silently.
  
          :param config: (:class:`.Config`) Configuration container.
          """
          non_null_params = ['space_id', 'access_token']
          for param in non_null_params:
              if getattr(config, param) is None:
                  raise Exception('Configuration for \"{0}\" must not be empty.'.format(param))
  
          for clazz in config.custom_entries:
              if not issubclass(clazz, Entry):
                  raise Exception(
                      'Provided class \"{0}\" must be a subclass of Entry.'.format(clazz.__name__))
              elif clazz is Entry:
                  raise Exception('Cannot register "Entry" as a custom entry class.')