code: function findPolicies(identifiers) {
    return loadPolicies()
    .then((policies) => {
      return _.filter(policies, (policy) => { return identifiers.indexOf(policy.name) !== -1; });
    });
  }
docs: Retrieve policies by their identifier
  @param {Array} identifiers - an array of policy identifiers
  @return {Promise<[Policy]>} - promise of an array of policies