function _assertValueLink(input) {
  _assertSingleLink(input);
  ("production" !== process.env.NODE_ENV ? invariant(
    input.props.value == null && input.props.onChange == null,
    'Cannot provide a valueLink and a value or onChange event. If you want ' +
    'to use value or onChange, you probably don\'t want to use valueLink.'
  ) : invariant(input.props.value == null && input.props.onChange == null));
}
@param {ReactComponent} input Form component
@return {*} current checked status of the input either from checked prop
            or link.