function isFlattenable(value) {
  return isArray(value) || isArguments(value) || !!(spreadableSymbol && value && value[spreadableSymbol]);
}
Checks if `value` is a flattenable `arguments` object or array.

@private
@param {*} value The value to check.
@returns {boolean} Returns `true` if `value` is flattenable, else `false`.