[Rust][Relay] nn.dense: is units a required parameter?

[gussmith23]

When parsing the following Relay expression:

#[version = "0.0.5"]
def @main(%data: Tensor[(16, 32), float32], %weights: Tensor[(64, 32), float32]) -> Tensor[(16, 64), float32] {
  nn.dense(%data, %weights)/* ty=Tensor[(16, 64), float32] */
}

I get:

thread 'language::from_relay::tests::dense' panicked at 'AttributeError: relay.attrs.DenseAttrs: Cannot find required field 'units' during initialization.If the key is defined check that its type matches the declared type.

Adding units=64 fixes the problem. However, the docs indicate that units is optional...at least in the Python frontend. Maybe units isn't optional in the text format?

(this is a new error -- I used to get the error detailed in #6470 when parsing nn.dense)

[masahi]

Let's continue at #7003