code: def _get_namespace(self, time=None) -> str:
      (
          names,
          metric_group_type,
      ) = self._get_metric_group_names_and_types()
      names.extend(metric_group_type)
      if time is not None:
          names.append(str(time))
      return json.dumps(names)
  
imports: import json
  from enum import Enum
  from typing import Callable, List, Tuple
  from pyflink.fn_execution.metrics.process.counter_impl import CounterImpl
  from pyflink.fn_execution.metrics.process.distribution_impl import DistributionImpl
  from pyflink.fn_execution.metrics.process.meter_impl import MeterImpl
  from pyflink.metrics import MetricGroup, Counter, Distribution, Meter
label_desc: Use image node_id 9 for calling the GenericMetricGroup obj's underlying member method code with example usage: obj._get_namespace(time) and returns: json