python: add type hints for enum sub-classes and sub-class `__init__`

methods.

uniffi_bindgen/src/bindings/python/templates/EnumTemplate.py

@@ -19,7 +19,11 @@ class {{ type_name }}:
     # Each enum variant is a nested class of the enum itself.
     {% for variant in e.variants() -%}
     class {{ variant.name()|enum_variant_py }}:
-        def __init__(self,{% for field in variant.fields() %}{{ field.name()|var_name }}{% if loop.last %}{% else %}, {% endif %}{% endfor %}):
+        {% for field in variant.fields() %}
+            {{- field.name()|var_name }}: "{{- field|type_name }}";
+        {%- endfor %}
+
+        def __init__(self,{% for field in variant.fields() %}{{ field.name()|var_name }}: "{{- field|type_name }}"{% if loop.last %}{% else %}, {% endif %}{% endfor %}):
             {% if variant.has_fields() %}
             {%- for field in variant.fields() %}
             self.{{ field.name()|var_name }} = {{ field.name()|var_name }}