change tif/tcc targets to be more variable

app/models/objective_function.py

@@ -1,12 +1,12 @@
 from pydantic import BaseModel
-from typing import Dict
+from typing import Dict, List
 
-from models.targets import Targets
+from models.target import Target
 
 class ObjectiveFunction(BaseModel):
   # minimizing tif/tcc target value is only option currently
   # as we add more we can build this out to be more dynamic
   # likely with models representing each objective function type
-  tif_targets: Targets
-  tcc_targets: Targets
+  tif_targets: List[Target]
+  tcc_targets: List[Target]
   weight: Dict = {'tif': 1, 'tcc': 1}