_getContenteditableElements(formElement) {
        if (AutoNumericHelper.isUndefinedOrNullOrEmpty(formElement) || !formElement.hasAttribute('id')) {
            return [];
        }
        const elementsInside = [...formElement.querySelectorAll('[contenteditable=true]')];
        const elementsOutside = [...document.querySelectorAll(`*:not(input)[form=${formElement.getAttribute('id')}][contenteditable=true]`)];

        return AutoNumericHelper.arrayUnique(elementsInside, elementsOutside);
    }
Returns an array of the non-input contenteditable elements linked to the given form element.
Two types of elements are possible, either located inside the form element, or outside.
For the outside elements, this only works if the form element has a defined id and that id is referenced on the non-input element as the `form` attribute.
If no elements can be found, then an empty array is returned.

@param {HTMLFormElement|null} formElement

@returns {Array.<HTMLInputElement>}
@private