metric_descriptor: <
  name: "ocagent.io/calls"
  description: "Number of calls"
  unit: "1"
  type: CUMULATIVE_INT64
  label_keys: <
    key: "empty_key"
  >
  label_keys: <
    key: "operation_type"
  >
>
timeseries: <
  start_timestamp: <
    seconds: 1543160298
    nanos: 100000090
  >
  label_values: <
    has_value: true
  >
  label_values: <
    value: "value_0"
    has_value: true
  >
  points: <
    timestamp: <
      seconds: 1543160298
      nanos: 101000090
    >
    int64_value: 1
  >
>
