code: def get_within_delta(key, app=None):
      
      txt = config_value(key, app=app)
      values = txt.split()
      return timedelta(**{values[1]: int(values[0])})
docs: Get a timedelta object from the application configuration following
      the internal convention of::
  
          <Amount of Units> <Type of Units>
  
      Examples of valid config values::
  
          5 days
          10 minutes
  
      :param key: The config value key without the 'SECURITY_' prefix
      :param app: Optional application to inspect. Defaults to Flask's
                  `current_app`