private boolean validateNegotiationMassChange(PersonMassChange personMassChange) {
    boolean isValid = true;

    NegotiationPersonMassChange negotiationPersonMassChange =
        personMassChange.getNegotiationPersonMassChange();

    if (negotiationPersonMassChange.isNegotiator()) {
      isValid &=
          validatePerson(personMassChange, NEGOTIATION_NEGOTIATOR_FIELD, NEGOTIATION_NEGOTIATOR);
    }

    return isValid;
  }