code: public org.mariadb.jdbc.internal.com.send.authentication.ed25519.math.GroupElement negate() {
      if (this.repr != Representation.P3) {
        throw new UnsupportedOperationException();
      }
      return this.curve.getZero(Representation.P3).sub(toCached()).toP3();
    }
docs: Negates this group element by subtracting it from the neutral group element.
  <p>
  TODO-CR BR: why not simply negate the coordinates $X$ and $T$?
  
  @return The negative of this group element.