Make name and model of State.__init__ optional

src/linkahead/common/state.py

@@ -137,7 +137,7 @@ class State:
         All transitions which are available from this state (read-only)
     """
 
-    def __init__(self, model: str, name: str):
+    def __init__(self, model: Optional[str], name: Optional[str]):
         self.name = name
         self.model = model
         self._id: Optional[str] = None
@@ -195,13 +195,7 @@ class State:
         -------
         state : State
         """
-        name = xml.get("name")
-        if name is None:
-            raise ValueError(f"State name is missing from xml:{str(xml)}")
-        model = xml.get("model")
-        if model is None:
-            raise ValueError(f"State model is missing from xml:{str(xml)}")
-        result = State(name=name, model=model)
+        result = State(name=xml.get("name"), model=xml.get("model"))
         result._id = xml.get("id")
         result._description = xml.get("description")
         transitions = [