Return a fully-qualified data_item string.

def data_item_path(cls, project, dataset, data_item):
        """Return a fully-qualified data_item string."""
        return google.api_core.path_template.expand(
            "projects/{project}/datasets/{dataset}/dataItems/{data_item}",
            project=project,
            dataset=dataset,
            data_item=data_item,
        )