docstr: Testing util method
docstr_tok: ["Testing","util","method"]
code: def cache_keys(self):
      """
      Testing util method
      """
      keys = []
      for metric_type, metric in self.cache.items():
          for metric_name in metric.keys():
              keys.append(f"{metric_type.value}:{metric_name}")
      return keys
  
file_path: serve/ts/metrics/metric_cache_yaml_impl.py
imports: import logging
  import yaml
  import ts.metrics.metric_cache_errors
  from ts.metrics.caching_metric import CachingMetric
  from ts.metrics.metric_cache_abstract import MetricCacheAbstract
  from ts.metrics.metric_type_enum import MetricTypes
label_desc: Use image node_id 7 for calling the MetricsCacheYamlImpl obj's underlying member method code with example usage: obj.cache_keys() and returns: keys