function _addOutOfBoundsClass(oob, addClasses, classes, classPrefix, outOfBoundsClass) {
  if (oob.length) {
    let oobClass;
    if (!isUndefined(outOfBoundsClass)) {
      oobClass = outOfBoundsClass;
    } else {
      oobClass = getClass('out-of-bounds', classes, classPrefix);
    }

    addClasses.push(oobClass);
    oob.forEach((side) => {
      addClasses.push(`${oobClass}-${side}`);
    });
  }
}
Add out of bounds classes to the list of classes we add to tether
@param {string[]} oob An array of directions that are out of bounds
@param {string[]} addClasses The array of classes to add to Tether
@param {string[]} classes The array of class types for Tether
@param {string} classPrefix The prefix to add to the front of the class
@param {string} outOfBoundsClass The class to apply when out of bounds
@private