code: public static Key<?> of(Parameter parameter)
    {
      return new Key(parameter.getParameterizedType(),
                     qualifiers(parameter.getAnnotations(),
                                parameter.getDeclaringExecutable().getAnnotations()));
    }
docs: Builds Key from parameter's parameterized type and and qualifying annotations
  found on the parameter and its declaring executable (e.g. Method)
  
  @param parameter parameter for deriving type and annotations from
  @return instance of a key