code: def _set_launcher_property(self, driver_arg_key, spark_property_key):
          
          value = self._spark_launcher_args.get(driver_arg_key, self.conf._conf_dict.get(spark_property_key))
          if value:
              self._spark_launcher_args[driver_arg_key] = value
              self.conf[spark_property_key] = value
docs: Handler for a special property that exists in both the launcher arguments and the spark conf dictionary.
  
          This will use the launcher argument if set falling back to the spark conf argument.  If neither are set this is
          a noop (which means that the standard spark defaults will be used).
  
          Since `spark.driver.memory` (eg) can be set erroneously by a user on the standard spark conf, we want to be able
          to use that value if present. If we do not have this fall-back behavior then these settings are IGNORED when
          starting up the spark driver JVM under client mode (standalone, local, yarn-client or mesos-client).
  
          Parameters
          ----------
          driver_arg_key : string
              Eg: "driver-memory"
          spark_property_key : string
              Eg: "spark.driver.memory"