code: public static Message.Builder addDefaultInstanceToRepeatedField(final Descriptors.FieldDescriptor repeatedFieldDescriptor, final Message.Builder builder) throws CouldNotPerformException {
          if (repeatedFieldDescriptor == null) {
              throw new NotAvailableException("repeatedFieldDescriptor");
          }
          return addDefaultInstanceToRepeatedField(repeatedFieldDescriptor.getName(), builder);
      }
docs: Method adds a new default message instance to the repeated field and return it's builder instance.
  @param repeatedFieldDescriptor The field descriptor of the repeated field.
  @param builder The builder instance of the message which contains the repeated field.
  @return The builder instance of the new added message is returned.
  @throws CouldNotPerformException