Comment in a Stream of Mapping

Hi,

Is the following Yaml valid?

```
---
# Comment
name: "eo-yaml"
version: 4.3.5
```

When I write it:

```
YamlNode node = Yaml.createYamlMappingBuilder()
.add("name", "eo-yaml")
.add("version", "4.3.5")
.build("Comment");
YamlStream expected = Yaml.createYamlStreamBuilder()
.add(node)
.build();
System.out.println(expected);
```

The comment does not appear:

```
---
name: "eo-yaml"
version: 4.3.5
```

Am I writing this Yaml wrong or maybe it is a little bug?

Thanks.