code: public JWTPayload setExpirationTimeSeconds(Long expirationTimeSeconds) {
          this.expirationTimeSeconds = expirationTimeSeconds;
          this.put(PayloadConstants.EXPIRATION_TIME_IN_SECS, expirationTimeSeconds);
          return this;
      }
docs: Sets the expiration time claim that identifies the expiration time (in seconds) on or after
  which the token MUST NOT be accepted for processing or {@code null} for none.
  
  <p>
  Overriding is only supported for the purpose of calling the super implementation and changing
  the return type, but nothing else.
  </p>