code: public void addSubtype(String subtype) {
      if(!StringUtils.isBlank(subtype) && !subtypes.contains(subtype.trim())) {
        subtypes.add(subtype.trim());
      }
    }
docs: Set the disambiguated entity subType.  SubTypes expose additional
  ontological mappings for a detected entity, such as identification of a
  Person as a Politician or Athlete.
  
  @param subtype disambiguated entity subType