I'm following [this alanstorm tutorial][1] and when I'm trying to load the backend page I've got this error:

> Fatal error: Uncaught Error: Class 'Mage_Antonino-banner_Helper_Data' not found

Probably there's some typo or some naming convention error, but I really cannot find it.

> app/code/local/Antonino/Banner/etc/config.xml 

    <?xml version="1.0" encoding="UTF-8" ?>
    <config>
        <modules>
            <Antonino_Banner>
                <version>1.0.0</version>
            </Antonino_Banner>
        </modules>
        <global>
            <models>
                <banner>
                    <class>Antonino_Banner_Model</class>
                </banner>
            </models>
            <helpers>
                <banner>
                    <class>Antonino_Banner_Helper</class>
                </banner>
            </helpers>
        </global>
    </config>
And 

> app/code/local/Antonino/Banner/etc/system.xml


    <?xml version="1.0" encoding="UTF-8" ?>
    <config>
        <tabs>
            <antonino_banner translate="label" module="antonino-banner">
                <label>Antonino</label>
                <sort_order>350</sort_order>
            </antonino_banner>
        </tabs>
        <sections>
            <antoninobanner translate="label" module="antonino-banner">
                <label>Banner Config Options</label>
                <tab>antonino_banner</tab>
                <frontend_type>text</frontend_type>
                <sort_order>300</sort_order>
                <show_in_default>1</show_in_default>
                <show_in_website>1</show_in_website>
                <show_in_store>1</show_in_store>
                <groups>
                    <general translate="label">
                        <label>General</label>
                        <frontend_type>text</frontend_type>
                        <sort_order>5</sort_order>
                        <show_in_default>1</show_in_default>
                        <show_in_website>1</show_in_website>
                        <show_in_store>1</show_in_store>
                        <fields>
                            <choose_category translate="label comment">
                                <label>Choose Category</label>
                                <comment>Select the category to which apply the banner</comment>
                                <frontend_type>select</frontend_type>
                                <source_model>banner/categories</source_model>
                                <show_in_default>1</show_in_default>
                                <show_in_website>1</show_in_website>
                                <show_in_store>1</show_in_store>
                            </choose_category>
                        </fields>
                    </general>
                    <anothergroup translate="label">
                        <label>Another Group</label>
                        <frontend_type>text</frontend_type>
                        <sort_order>5</sort_order>
                        <show_in_default>1</show_in_default>
                        <show_in_website>1</show_in_website>
                        <show_in_store>1</show_in_store>
                    </anothergroup>
                </groups>
            </antoninobanner>
            <antoninobannertwo translate="label" module="antonino-banner">
                <label>Another section</label>
                <tab>antonino_banner</tab>
                <frontend_type>text</frontend_type>
                <sort_order>300</sort_order>
                <show_in_default>1</show_in_default>
                <show_in_website>1</show_in_website>
                <show_in_store>1</show_in_store>
            </antoninobannertwo>
        </sections>
    </config>
The error shows when I use the method `Mage::helper('banner')->__('Hello')` in `app/code/local/Antonino/Banner/Model/Categories.php` which code is 

    <?php
        
    class Antonino_Banner_Model_Categories extends Mage_Core_Helper_Abstract
    {
        public function toOptionArray()
        {
            return array(
                array('value'=>1, 'label'=>Mage::helper('banner')->__('Hello')),
                array('value'=>2, 'label'=>Mage::helper('banner')->__('Goodbye')),
                array('value'=>3, 'label'=>Mage::helper('banner')->__('Yes')),
                array('value'=>4, 'label'=>Mage::helper('banner')->__('No')),
            );
        }
    
    }

Someone could pls help me? I really cannot figure out why this is not working. 
Thanks!

  [1]: http://alanstorm.com/custom_magento_system_configuration/