@Override
  public boolean validateConstraint(Set<String> sourceTags,
      PlacementConstraint placementConstraint) {
    if (!validateSourceTags(sourceTags)) {
      return false;
    }
    // TODO: Perform actual validation of the constraint (in YARN-6621).
    // TODO: Perform satisfiability check for constraint.
    return true;
  }
@Test
  public void testValidateConstraint() {
    // At the moment we only disallow multiple source tags to be associated with
    // a constraint. TODO: More tests to be added for YARN-6621.
    Assert.assertTrue(pcm.validateConstraint(sourceTag1, c1));
    Assert.assertFalse(pcm.validateConstraint(sourceTag4, c1));
  }