public static BasicPolicyMemento.Builder newPolicyMementoBuilder(Policy policy) {
    BasicPolicyMemento.Builder builder = BasicPolicyMemento.builder();

    builder.type = policy.getClass().getName();
    builder.typeClass = policy.getClass();
    builder.id = policy.getId();
    builder.displayName = policy.getName();

    // TODO persist config keys as well? Or only support those defined on policy class;
    // current code will lose the ConfigKey type on rebind for anything not defined on class.
    // Whereas entities support that.
    // TODO Do we need the "nonPersistableFlagNames" that locations use?
    Map<ConfigKey<?>, Object> config = ((AbstractPolicy) policy).getConfigMap().getAllConfig();
    for (Map.Entry<ConfigKey<?>, Object> entry : config.entrySet()) {
      ConfigKey<?> key = checkNotNull(entry.getKey(), "config=%s", config);
      Object value = configValueToPersistable(entry.getValue());
      builder.config.put(key.getName(), value);
    }

    Map<String, Object> persistableFlags =
        MutableMap.<String, Object>builder()
            .putAll(
                FlagUtils.getFieldsWithFlagsExcludingModifiers(
                    policy, Modifier.STATIC ^ Modifier.TRANSIENT))
            .remove("id")
            .remove("name")
            .build();
    builder.config.putAll(persistableFlags);

    return builder;
  }
  /**
   * finds the policy indicated by the given ID or name.
   *
   * @see {@link getPolicy(String,String,String)}.
   *     <p>
   * @throws 404 or 412 (unless input is null in which case output is null)
   */
  public Policy getPolicy(Entity entity, String policy) {
    if (policy == null) return null;

    for (Policy p : entity.getPolicies()) {
      if (policy.equals(p.getId())) return p;
    }
    for (Policy p : entity.getPolicies()) {
      if (policy.equals(p.getName())) return p;
    }

    throw WebResourceUtils.notFound("Cannot find policy '%s' in entity '%s'", policy, entity);
  }