message: Adding a comment for metrictype values
diff: @@ -3,6 +3,8 @@ import FormData from './FormData';
  export const LABEL_MAX_LENGTH = 43;
  +// Note that the values of MetricKeys are lower_snake_case because they're
  +// used as keys of form data jsons.
  export enum MetricKey {
  METRIC = 'metric',
  METRICS = 'metrics',
  