function ensureArrayAndPush(object, key, value) {
			if (!Array.isArray(object[key])) {
				object[key] = [];
			}
			object[key].push(value);
		}
Ensure that an array exists at [key] on `object`, and add `value` to it.
@param {Object} object the object to mutate
@param {string} key the object's key
@param {any} value the value to add
@returns {void}
@private