@Override
    public int hashCode() {
        return Objects.hash(properties);
    }
Get a property and throw if it isn't present.

@param property property key to get by exact reference identity.
@param <T> value type of the property.
@throws IllegalArgumentException if the property isn't found.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/TypedPropertiesBag.java