code: def init_app(self, app):
          
  
          if self.__inited:
              return
  
          config = app.config.get(
              'FLASK_LOGGING_EXTRAS', {})
  
          blueprint_config = config.get('BLUEPRINT', {})
          self.bp_var = blueprint_config.get('FORMAT_NAME', 'blueprint')
          self.bp_app = blueprint_config.get('APP_BLUEPRINT', '<app>')
          self.bp_noreq = blueprint_config.get('NO_REQUEST_BLUEPRINT', '<not a request>')
  
          for var_name, resolver_fqn in config.get('RESOLVERS', {}).items():
              if resolver_fqn is None:
                  resolver = None
              else:
                  try:
                      resolver = _import_by_string(resolver_fqn)
                  except ImportError:
                      resolver = resolver_fqn
  
              self.resolvers[var_name] = resolver
  
              self.__inited = True
docs: Initialise the formatter with app-specific values from ``app``’s configuration