default boolean isPresent() {
        return true;
    }
Checks if the attribute value is considered present.

<p>Attribute value are considered present if they are not null. If the
attribute value is a projection, then it is considered present if it is
not empty.

@return Returns true if present.
smithy-model/src/main/java/software/amazon/smithy/model/selector/AttributeValue.java