code: public List<List<String>> getPolicy(String sec, String ptype) {
          return model.get(sec).get(ptype).policy;
      }
docs: getPolicy gets all rules in a policy.
  
  @param sec the section, "p" or "g".
  @param ptype the policy type, "p", "p2", .. or "g", "g2", ..
  @return the policy rules of section sec and policy type ptype.