added from_choice classmethod

src/model_textual/classes.py

@@ -1,4 +1,4 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, ValidationError
 from typing import List
 import random
 
@@ -20,6 +20,18 @@ class ModelOutput(BaseModel):
         """Instantiate with random numbers."""
         kwargs = {field: random.random() for field in cls.list_fields()}
         return cls(**kwargs)
+    
+    @classmethod
+    def from_choice(cls, option: str):
+        """Instantiate from choice."""
+        if option is None:
+            raise ValidationError()
+        assert isinstance(option, str)
+        allowed_options_list = cls.list_fields()
+        assert option in allowed_options_list, f"{option} is not among allowed fields {allowed_options_list}"
+        kwargs = {field: 0 for field in cls.list_fields()}
+        kwargs[option] = 1
+        return cls(**kwargs)
 
     def __repr__(self) -> str:
         model_dict = self.model_dump()