Docs: Provide YAML example to Variant

Signed-off-by: Gunnar Andersson <[email protected]>

ifex/model/ifex_ast.py

@@ -418,8 +418,7 @@ class Typedef:
     """
     Dataclass used to represent IFEX Typedef.
 
-    Each typedef is an alias to an existing fundamental type, defined type, or enumerator, giving it an additional name.
-    The new data type can be used by other datatypes, method & event parameters, and properties.
+    A Typedef is an alias to an existing fundamental type or defined type, including structs, enumerators, etc.  It can also be used to name and define a variant type.  The new data type name can be used in the definition of other datatypes, method- and event-parameters, and properties.
 
     A typedefs list object example is given below:
 
@@ -432,10 +431,22 @@ class Typedef:
         description: The movement of a seat component
     ```
 
-    Variant types:
+    **Variant types**
 
     The fields `datatype` and `datatypes` are mutually exclusive - only one of them may have a value.  The field `datatypes` is used to specify multiple types associated with this type name.  Doing this makes it a `variant` type.  It is also possible to define a variant type using the `variant<a,b,c>`-style syntax in any location requiring a datatype, but the ability to specify it as a list can be more useful if the number of types is large.  Handling this as a list can also allow Layers to extend a variant type more conveniently.
 
+    ```yaml
+    typedefs:
+      - name: StringOrStruct
+        datatypes:
+          - string
+          - MyStruct
+          - OtherStruct
+        description: The Thing, represented in one of 3 ways.
+    ```
+
+    **NOTE!** The fields `datatype` and `datatypes` are defined as optional in the language model, but one of them must be defined.
+
     """
 
     name: str