tcc and tif drift, compensated for string value casing, csv to dict improved process

app/models/solver_run.py

@@ -9,7 +9,7 @@ from models.objective_function import ObjectiveFunction
 from models.advanced_options import AdvancedOptions
 
 class SolverRun(BaseModel):
-  items: List[Item]
+  items: List[Item] = []
   bundles: Optional[Bundle]
   constraints: List[Constraint]
   irt_model: IRTModel
@@ -63,3 +63,6 @@ class SolverRun(BaseModel):
               count=1,
               type=type_attribute
             )]
+
+  def get_constraint(self, name):
+    return next((constraint for constraint in self.constraints if constraint.reference_attribute.id == name), None)