need AnyStr to set value on pydantic model

app/models/objective_function.py

@@ -1,5 +1,5 @@
 from pydantic import BaseModel
-from typing import Dict, List
+from typing import Dict, List, AnyStr
 
 from models.target import Target
 
@@ -9,5 +9,5 @@ class ObjectiveFunction(BaseModel):
   # likely with models representing each objective function type
   tif_targets: List[Target]
   tcc_targets: List[Target]
-  objective: "minimize"
+  objective: AnyStr = "minimize"
   weight: Dict = {'tif': 1, 'tcc': 1}