Caller form datasource access in child form - Dynamics 365 for operations

Requirement: When you click on view details on vendor bank account, Vendor bank accounts form should filter based on vendor selected in purchase agreement.

Solution: In Microsoft dynamics 365 for operations we customize using extension approach.

1. Create post event handler for init method for VendBankAccounts form.

               [PostHandlerFor( formStr(VendBankAccounts),