docs: public TypeSignature getTypeSignature() {
          if (typeSignatureStr == null) {
              return null;
          }
          if (typeSignature == null) {
              try {
                  typeSignature = TypeSignature.parse(typeSignatureStr, declaringClassName);
                  typeSignature.setScanResult(scanResult);
              } catch (final ParseException e) {
                  throw new IllegalArgumentException(e);
              }
          }
          return typeSignature;
      }