def _get_dep_values(
        self, used_task_invocations: Mapping[str, tuple[str, ...]]
    ) -> dict[str, str]:
        """
        Get env vars from upstream tasks declared via the uses option.
        """
        return {
            var_name: self.get_task_output(invocation)
            for var_name, invocation in used_task_invocations.items()
        }

        Get env vars from upstream tasks declared via the uses option.
        
poethepoet/context.py