assert formatting

[lezcano]

In this commit, yapf formats the long line

    assert f32_backend.lower() in builder.options.allowed_dot_f32_backends, f"f32 _backend must be one of {builder.options.allowed_dot_f32_backends}. Got {f32_backend}"

within semantic.py as

    assert f32_backend.lower(
    ) in builder.options.allowed_dot_f32_backends, f"f32 _backend must be one of {builder.options.allowed_dot_f32_backends}. Got {f32_backend}"

resulting in a syntax error.