code: private <T> void addDelegatorField(T delegator, final CtClass replicaClass) throws CannotCompileException {
          CtField f = CtField.make(String.format("private %s %s = null;", delegator.getClass().getName(),
                  POWERMOCK_INSTANCE_DELEGATOR_FIELD_NAME), replicaClass);
          replicaClass.addField(f);
      }
docs: Add a field to the replica class that holds the instance delegator. I.e.
  if we're creating a instance replica of {@code java.lang.Long} this
  methods adds a new field of type {@code delegator.getClass()} to the
  replica class.