code: public boolean alreadyExists(String tangoHost) throws DevFailed {
          String  header = "tango://"+tangoHost+"/";
  
          //  Check if server defined in database.
          try {
              new DeviceProxy(header + "dserver/"+serverName.toLowerCase());
              return true;
          }
          catch (DevFailed e){ /* Does not exist. --> Continue */ }
  
          //  Check if at least one device already defined
          for (TangoClass clazz : classes) {
              for (TangoDevice device : clazz) {
                  try {
                      new DeviceProxy(header+device.name);
                      return true;
                  }
                  catch (DevFailed e) {
                      if (!e.errors[0].desc.contains("not defined in the database"))
                          Except.re_throw_exception(e, "FailedToCheck",
                                  "Failed to check " + device.name +  "in " + tangoHost,
                                  "DbServerStructure.alreadyExists()");
                  }
              }
          }
          return false;
      }
docs: ===============================================================