code: def get_error_key(name, unit):
      dimensions = list()
      dimensions.append(Dimension("Level", "Error"))
      dim_str = [name, unit, "None"] + [str(d) for d in dimensions]
      return "-".join(dim_str)
  
file_path: serve/ts/tests/unit_tests/test_backend_metric.py
imports: import logging
  import sys
  import pytest
  from ts.metrics.dimension import Dimension
  from ts.metrics.metrics_store import MetricsStore
  from ts.service import emit_metrics
label_desc: Use image node_id 2 for calling a global function with example usage: get_error_key(name, unit) and returns: str