def by_contact_folder_id1(self,contact_folder_id1: str) -> ContactFolderItemRequestBuilder:
        """
        Provides operations to manage the childFolders property of the microsoft.graph.contactFolder entity.
        param contact_folder_id1: The unique identifier of contactFolder
        Returns: ContactFolderItemRequestBuilder
        """
        if contact_folder_id1 is None:
            raise TypeError("contact_folder_id1 cannot be null.")
        from .item.contact_folder_item_request_builder import ContactFolderItemRequestBuilder

        url_tpl_params = get_path_parameters(self.path_parameters)
        url_tpl_params["contactFolder%2Did1"] = contact_folder_id1
        return ContactFolderItemRequestBuilder(self.request_adapter, url_tpl_params)

        Provides operations to manage the childFolders property of the microsoft.graph.contactFolder entity.
        param contact_folder_id1: The unique identifier of contactFolder
        Returns: ContactFolderItemRequestBuilder
        
msgraph/generated/users/item/contact_folders/item/child_folders/child_folders_request_builder.py