static AttributesBuilder builder(AttributesGetters parent) {
        requireNonNull(parent, "parent");
        return new ImmutableAttributesBuilder(parent);
    }
Returns a new empty {@link AttributesBuilder}.
The parent {@link Attributes} can be accessed via {@link #attr(AttributeKey)} or {@link #attrs()}.

<p>Note that any mutations in {@link AttributesBuilder} won't modify the attributes in the parent.
core/src/main/java/com/linecorp/armeria/common/Attributes.java