private Shape RetrieveCategoryNameBox(PowerPointSlide slide)
        {
            var nameBoxCandidate = slide.GetShapesWithTypeAndRule(MsoShapeType.msoTextBox, new Regex(".+"));

            if (nameBoxCandidate.Count == 0)
            {
                return null;
            }

            var categoryNamePattern = new Regex(CategoryNameBoxSearchPattern);

            // return the first match name box
            return nameBoxCandidate.FirstOrDefault(x => categoryNamePattern.IsMatch(x.TextFrame.TextRange.Text));
        }