docs: private int getIndex(TypeVariable<?> variable) {
  
          Class<?> rawType = resolveClass(owningType);
          TypeVariable<?>[] typeParameters = rawType.getTypeParameters();
  
          for (int i = 0; i < typeParameters.length; i++) {
              if (variable.equals(typeParameters[i])) {
                  return i;
              }
          }
  
          return -1;
      }