import inspect


def get_transformer_name(transformer):
    """Return the fully qualified path of the transformer.

    Args:
        transformer:
            A transformer class.

    Raises:
        ValueError:
            Crashes when the transformer is not passed as a class.

    Returns:
        string:
            The path of the transformer.
    """
    if inspect.isclass(transformer):
        return transformer.__module__ + '.' + transformer.__name__

    raise ValueError(f'The transformer {transformer} must be passed as a class.')