code: synchronized final JsMsgPart getHdr2() {
          if (hdr2 == null) {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                  SibTr.debug(this, tc, "getHdr2 will call getPart");
              hdr2 = jmo.getPart(JsHdrAccess.HDR2, JsHdr2Access.schema);
          }
          return hdr2;
      }
docs: Get the JsMsgPart which contains the JMF Message described by the
  JsHdr2 schema.
  Once obtained, the value is cached, and the cached value is returned until
  the cache is cleared.
  
  @return JsMsgPart The message part described by the JsHdr2 schema