@Override
  public Set<String> getInputMetrics() {
    return inputMetricKeys;
  }
@Test
  public void input_metrics_is_empty_when_not_set() {
    MeasureComputer.MeasureComputerDefinition measureComputer = new MeasureComputerDefinitionImpl.BuilderImpl()
      .setOutputMetrics("comment_density_1", "comment_density_2")
      .build();

    assertThat(measureComputer.getInputMetrics()).isEmpty();
  }