code: def _get_or_add_metric(
      self, metric_name, unit, dimensions, metric_type
  ) -> MetricAbstract:
      try:
          metric = self.get_metric(metric_name, metric_type)
      except merrors.MetricsCacheKeyError:
          metric = self.add_metric_to_cache(
              metric_name=metric_name,
              unit=unit,
              metric_type=metric_type,
              dimension_names=[dim.name for dim in dimensions],
          )
      return metric
  
imports: import abc
  import os
  import ts.metrics.metric_cache_errors
  from ts.metrics.dimension import Dimension
  from ts.metrics.metric_abstract import MetricAbstract
  from ts.metrics.metric_type_enum import MetricTypes
label_desc: Use image node_id 11 for calling the MetricCacheAbstract obj's underlying member method code with example usage: obj._get_or_add_metric(metric_name, unit, dimensions, metric_type) and returns: metric