Trying to insert values to widget_instance_page table entities column through custom import

I am trying to create a custom import through which I am trying to add a product id to the entities column.

Whenever I do import a new entry is created as in the below image, whereas I need the product id to be updated in the entities column with comma separated value.

Using the code given in the below link
https://bsscommerce.com/confluence/how-to-magento-2-import-csv-file-to-custom-table/