function isValidListener (listener) {
        if (typeof listener === 'function' || listener instanceof RegExp) {
            return true
        } else if (listener && typeof listener === 'object') {
            return isValidListener(listener.listener)
        } else {
            return false
        }
    }
Fetches the requested listeners via getListeners but will always return the results inside an object. This is mainly for internal use but others may find it useful.

@param {String|RegExp} evt Name of the event to return the listeners from.
@return {Object} All listener functions for an event in an object.