@Override
        public ShapeId getShapeId() {
            return ID;
        }
Indicates that a string value must contain a valid shape ID.

<p>{@code failWhenMissing} can be set to true to fail when the
shape ID contained in a string shape cannot be found in the result
set of the {@code selector} property. {@code failWhenMissing} defaults to
{@code false} when not set.

<p>The {@code selector} property is used to query the model for all shapes
that match a shape selector. The value contained within the string shape
targeted by this trait MUST match one of the shapes returns by the shape
selector if {@code failWhenMissing} is set to true. {@code selector}
defaults to "*" when not set.
smithy-model/src/main/java/software/amazon/smithy/model/traits/IdRefTrait.java