How do I pass an array of values to a parsleyJS validateMultiple validator?

I want to validate a "true/false" requirement on grouped radio inputs using parsleyjs.

I have applied a multiple attribute data-parsley-multiple="my_input_group" so that they will validate together if required, however I am unsure how to create a custom validator to ensure the value is True and not False.

<div class="custom-control custom-radio custom-control-inline">
  <input 
    type="radio" id="customRadioInline1" name="customRadioInline1" class="custom-control-input" 
    value="True" data-parsley-multiple="my_input_group">
  <label class="custom-control-label" for="customRadioInline1">Yes</label>
</div>
<div class="custom-control custom-radio custom-control-inline">
  <input 
    type="radio" id="customRadioInline2" name="customRadioInline1" class="custom-control-input" 
    value="False" data-parsley-multiple="my_input_group">
  <label class="custom-control-label" for="customRadioInline2">No</label>
</div>

I think the way to do it is using validateMultiple to pass an array to a custom validator, however there are no examples in the docs as to how I achieve this. For example, if I add data-parsley-myvalidator=true to each input and use:

window.Parsley.addValidator('myvalidator', {
  requirementType: 'integer',
  validateMultiple(values, requirement, instance) {
    console.log('values', values);
    return true;
  },
  messages: {
    en: "'Yes' required.",
  },
});

I get:

Uncaught Validator undefined only handles multiple values

How do I pass an array of values to a validateMultiple custom validator?