Make the gradient limits automatically adapt to local conditions.

Input parameters:

1. Gr → Gradient to modify.
2. Lo → If true, the lower gradient limit will automatically adapt to local conditions. If false, the lower gradient limit remains constant. If omitted, the existing lower limit behaviour remains intact.
3. Up → If true, the upper gradient limit will automatically adapt to local conditions. If false, the upper gradient limit remains constant. If omitted, the existing upper limit behaviour remains intact.

Output parameters:

1. Gr → Modified gradient.