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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def CreateCounterMetadata(metric_name, fields=None, docstring=None, units=None):
 """Helper function for creating MetricMetadata for counter metrics."""

  return rdf_stats.MetricMetadata(
      varname=metric_name,
      metric_type=rdf_stats.MetricMetadata.MetricType.COUNTER,
      value_type=rdf_stats.MetricMetadata.ValueType.INT,
      fields_defs=FieldDefinitionProtosFromTuples(fields or []),
      docstring=docstring,
      units=units)