code: public PID getPID() {
          if (pid == null) {
              // The pid of Management.ingest is provided by the return value
              if (methodName.equals("ingest")) {
                  pid = PID.getInstance((String)returnVal);
              } else {
                  // Relationship methods specify a subject, which may be
                  // pid (deprecated), Fedora object URI or datastream URI
                  if (methodName.contains("Relationship")) {
                      String subject = (String)getParameter("subject");
                      // info:fedora URI?
                      if (subject.startsWith(Constants.FEDORA.uri)) {
                          pid = PID.getInstance(subject.split("/", 3)[1]);
                      } else { // not a URI, assume pid
                          pid = PID.getInstance(subject);
                      }
                  } else {
                      pid = PID.getInstance((String)getParameter("pid"));
                  }
              }
          }
          return pid;
      }
docs: Get the <code>PID</code> of this method.
  @return The <code>PID</code> or null.