code: public boolean removePolicy(String sec, String ptype, List<String> rule) {
          for (int i = 0; i < model.get(sec).get(ptype).policy.size(); i ++) {
              List<String> r = model.get(sec).get(ptype).policy.get(i);
              if (Util.arrayEquals(rule, r)) {
                  model.get(sec).get(ptype).policy.remove(i);
                  return true;
              }
          }
  
          return false;
      }
docs: removePolicy removes a policy rule from the model.
  
  @param sec the section, "p" or "g".
  @param ptype the policy type, "p", "p2", .. or "g", "g2", ..
  @param rule the policy rule.
  @return succeeds or not.