whole_func_string: function eventBinderCheck(key, fn) {
    if (!chimeeHelper.isString(key)) throw new TypeError('key parameter must be String');
    if (!chimeeHelper.isFunction(fn)) throw new TypeError('fn parameter must be Function');
  }
func_code_string: function eventBinderCheck(key, fn) {
    if (!chimeeHelper.isString(key)) throw new TypeError('key parameter must be String');
    if (!chimeeHelper.isFunction(fn)) throw new TypeError('fn parameter must be Function');
  }
func_documentation_string: checker for on, off, once function
  @param {string} key
  @param {Function} fn