code: @SuppressWarnings("unchecked")
      public static <T> Constructor<T> constructor(Class<T> declaringClass) {
          return (Constructor<T>) WhiteboxImpl.findConstructorOrThrowException(declaringClass);
      }
docs: Returns any one constructor specified in declaringClass. Is is useful when you only have ONE constructor
  declared in {@code declaringClass} but you don't care which parameters it take.
  
  @param declaringClass
  The declaringClass of the class where the constructor is
  located.
  @return A {@code java.lang.reflect.Constructor}.
  @throws TooManyConstructorsFoundException
  If more than one constructor was present in
  {@code declaringClass}