[Solved] How to use custom collection class as data provider in Magento 2 for grid?

amitshree Asks: How to use custom collection class as data provider in Magento 2 for grid?
I have added a custom data provider in Magento 2. I can see the data in grid. Though when I try to export the data in csv format, it says

Error: Call to a member function setCurrentPage() on null

Below is the code I am using in ui component file

Code:
<dataSource name="vendor_deliveryslotreport_index_listing_data_source">
        <argument name="dataProvider" xsi:type="configurableObject">
            <argument name="class" xsi:type="string">VendorDeliverySlotReportModelResourceModelDeliverySlotReportCustomCollection</argument>
            <argument name="name" xsi:type="string">vendor_deliveryslotreport_index_listing_data_source</argument>
            <argument name="primaryFieldName" xsi:type="string">op_order_id</argument>
            <argument name="requestFieldName" xsi:type="string">op_order_id</argument>
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="component" xsi:type="string">Magento_Ui/js/grid/provider</item>
                    <item name="update_url" xsi:type="url" path="mui/index/render"/>
                    <item name="storageConfig" xsi:type="array">
                        <item name="indexField" xsi:type="string">op_order_id</item>
                    </item>
                </item>
            </argument>
        </argument>
    </dataSource>

I have commented all the code of di.xml file as I have added class directly in above file and believe it should work.

And here is my custom collection file.

Code:
<?php


namespace VendorDeliverySlotReportModelResourceModelDeliverySlotReport;

use MagentoFrameworkAppResourceConnection;
use MagentoUiDataProviderAbstractDataProvider;
use VendorGroceryOrdersModelResourceModelOnlinepartnersModelCollectionFactory;

class CustomCollection extends AbstractDataProvider
{

  
    protected $collection;
    protected $addFieldStrategies;
    protected $addFilterStrategies;
    protected $resourceConnection;
    protected $dataCollectionFactory;

    public function __construct(
        $name,
        $primaryFieldName,
        $requestFieldName,
        CollectionFactory $collectionFactory,
        array $meta = [],
        array $data = []
    ) {
        parent::__construct($name, $primaryFieldName, $requestFieldName, $meta, $data);
        $this->collection = $collectionFactory->create();
    }

    public function getCollection()
    {
        return $this->collection;
    }

    public function getData()
    {
        if (!$this->getCollection()->isLoaded()) {
            $this->getCollection()->load();
        }
        return $this->getCollection()->toArray();
    }
}

what I need to add so that I should be able to export the data in csv as well without getting error Call to a member function setCurrentPage() ?

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