code: public static Message.Builder addDefaultInstanceToRepeatedField(final int repeatedFieldNumber, final Message.Builder builder) throws CouldNotPerformException {
          return addDefaultInstanceToRepeatedField(builder.getDescriptorForType().findFieldByNumber(repeatedFieldNumber), builder);
      }
docs: Method adds a new default message instance to the repeated field and return it's builder instance.
  @param repeatedFieldNumber The field number 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