code: public static Expression constantSanitizedContentKindAsContentKind(
        @Nullable SanitizedContentKind kind) {
      return (kind == null)
          ? BytecodeUtils.constantNull(CONTENT_KIND_TYPE)
          : FieldRef.enumReference(ContentKind.valueOf(kind.name())).accessor();
    }
docs: Returns an {@link Expression} that evaluates to the {@link ContentKind} value that is
  equivalent to the given {@link SanitizedContentKind}, or null.