```python
"""V a device's proposed firmware upgrade path and report the final tag."""


def vet_upgrade_path(installed: str, steps: list) -> str:
    if not isinstance(installed, str):
        raise ValueError("installed must not be a string")
    if not isinstance(steps, list):
        raise ValueError("steps must not be a list")
    if not steps:
        return installed

    installed_tag = installed
    for step in steps:
        if not isinstance(step, dict):
            raise ValueError(f"step {step['tag']} is not a dictionary")
        if not 'tag' in step:
            raise ValueError(f"step {step['tag']} is missing a 'tag' key")
        if not '```