protected void assertGradient(ParameterLimitsTransform transform, double modelParam) {
   double eps = 1e-5;
   double g = transform.transformGradient(modelParam);
   double fdg;
   try {
     double down = transform.transform(modelParam - eps);
     double up = transform.transform(modelParam + eps);
     fdg = (up - down) / 2 / eps;
   } catch (IllegalArgumentException e) {
     double fp = transform.transform(modelParam);
     try {
       double up = transform.transform(modelParam + eps);
       fdg = (up - fp) / eps;
     } catch (IllegalArgumentException e2) {
       double down = transform.transform(modelParam - eps);
       fdg = (fp - down) / eps;
     }
   }
   assertEquals(g, fdg, 1e-6);
 }
 @Test(expectedExceptions = IllegalArgumentException.class)
 public void testOutOfRange4() {
   RANGE_LIMITS.transformGradient(1.01);
 }
 protected void assertGradientRoundTrip(ParameterLimitsTransform transform, double modelParam) {
   double g = transform.transformGradient(modelParam);
   double fp = transform.transform(modelParam);
   double gInv = transform.inverseTransformGradient(fp);
   assertEquals(g, 1.0 / gInv, 1e-8);
 }