YAML conversions expect any UCG value.
They are transformed into toml using the following rules:
- tuples become maps `{...}`
- lists become lists `[...]`
- Int becomes an Int
- Float becomes a Float
- Strings become Strings.
- Functions and Modules are ignored.
If you are using the yamlmulti conversion type then a list will get transformed
into a yaml document per list item. All other types will get treated as a single
document.