public ExportGroupBuilder attr(String alias, AttributeKey<?> attrKey, Function<?, String> stringifier) {
        requireNonNull(alias, "alias");
        requireNonNull(attrKey, "attrKey");
        requireNonNull(stringifier, "stringifier");
        attrs.add(new ExportEntry<>(attrKey, alias, stringifier));
        return this;
    }
Adds the specified {@link AttributeKey} to the export list.
The specified {@code alias} is used for the export key.

@param alias the alias of the attribute to export
@param attrKey the key of the attribute to export
@param stringifier the {@link Function} that converts the attribute value into a {@link String}
core/src/main/java/com/linecorp/armeria/common/logging/ExportGroupBuilder.java