code: private File nameToFile(String policyName) throws PolicyIndexException {
          PID pid;
          try {
              pid = new PID(policyName);
          } catch (MalformedPIDException e) {
              throw new PolicyIndexException("Invalid policy name.  Policy name must be a valid PID - " + policyName);
          }
          return new File(DB_HOME + "/" + pid.toFilename() + ".xml");
  
      }
docs: Convert a policy name to a filename that can be used to persist the policy.
  Policy names must be valid PIDs (the DO managing the policy)
  @param policyName
  @return
  @throws PolicyIndexException