code: @NotNull
      public Rational getSimplifiedInstance()
      {
          long gcd = GCD(_numerator, _denominator);
  
          return new Rational(_numerator / gcd, _denominator / gcd);
      }
docs: <p>
  Simplifies the representation of this {@link Rational} number.</p>
  <p>
  For example, 5/10 simplifies to 1/2 because both Numerator
  and Denominator share a common factor of 5.</p>
  <p>
  Uses the Euclidean Algorithm to find the greatest common divisor.</p>
  
  @return A simplified instance if one exists, otherwise a copy of the original value.