code: def emit(self, metric_data: MetricData):
      self.metric_data[metric_data.name] = metric_data
  
imports: import abc
  import unittest.mock
  from torch.distributed.elastic.metrics.api import MetricData, MetricHandler, MetricStream, _get_metric_name, prof
  from torch.testing._internal.common_utils import run_tests, TestCase
label_desc: Use image node_id 2 for calling the TestMetricsHandler obj's underlying member method code with example usage: obj.emit(metric_data) without return types